Image sensor and image-capturing device

ABSTRACT

An image sensor includes: first pixels, each of which receives a pair of light fluxes and outputs a pair of first analog signals; an A/D conversion unit that converts each of pairs of first analog signals to a pair of first digital signals; a digital adder unit that generates digital sum signals each by adding together the pair of first digital signals among pairs of first digital signals; a first output unit that outputs pairs of first digital signals to an external recipient; and a second output unit that outputs the digital sum signals to an external recipient.

TECHNICAL FIELD

The present invention relates to an image sensor and an image-capturingdevice.

BACKGROUND ART

Image capturing devices known in the related art include theimage-capturing device disclosed in patent literature 1. Theimage-capturing device includes an image sensor disposed on apredetermined focal plane of a photographic lens (optical system). Theimage sensor has arrayed thereat focus detection pixels, eachconstituted with a micro-lens and a pair of photoelectric conversionunits disposed to the rear of the micro-lens. A pair of image signalscorresponding to a pair of images formed with a pair of focus detectionlight fluxes passing through the optical system are generated as analogsignals via the pair of photoelectric conversion units. The pair ofanalog signals are read out from the image sensor independently of eachother and the focusing condition (defocus amount) at the photographiclens is detected by detecting an image shift amount (phase difference)indicating the extent of image shift manifested by the pair of imagesignals. Image information is generated as the analog signals, generatedat the pair of photoelectric conversion units in each focus detectionpixel, are analogously added together within the focus detection pixeland the analog signal resulting from the addition is read out as animage signal from the image sensor.

CITATION LIST Patent Literature

PTL1: Japanese Laid Open Patent Publication No. 2001-83407

SUMMARY OF INVENTION Technical Problem

In an image-capturing device such as that described above, the pair ofanalog signals undergo analog addition processing within the focusdetection pixel. This means that while the pair of analog signals needto be read out independently of each other from the image sensor forfocus detection operation, the pair of analog signals must be firstadded together and read out as the sum resulting from the addition fromthe image sensor in order to generate image information. Namely, thereis an issue in that focus detection and image information generationcannot be executed at once when reading out signals for a given framefrom the image sensor.

Solution to Problem

An image sensor according to a first aspect of the present inventioncomprises: first pixels, each of which receives a pair of light fluxesand outputs a pair of first analog signals; an A/D conversion unit thatconverts each of pairs of first analog signals to a pair of firstdigital signals; a digital adder unit that generates digital sum signalseach by adding together the pair of first digital signals among pairs offirst digital signals; a first output unit that outputs pairs of firstdigital signals to an external recipient; and a second output unit thatoutputs the digital sum signals to an external recipient.

According to a second aspect of the present invention, in the imagesensor according to the first aspect, it is preferable to furthercomprise: a pixel array unit that includes first pixel groups eachformed with the first pixels disposed along a first direction, with thefirst pixel groups set side-by-side along a second directionintersecting the first direction; and a scanning unit that scans thefirst pixel groups in the pixel array unit along the second direction.The A/D conversion unit converts the pairs of first analog signalsoutput via the first pixels, disposed in a first pixel group beingscanned by the scanning unit, to the pairs of first digital signals inparallel within the first pixel group.

According to a third aspect of the present invention, in the imagesensor according to the second aspect, it is preferable that the pixelarray unit further includes second pixels, each of which receives alight flux and outputs a second analog signal; the first pixel groupseach include the first pixels and the second pixels disposed along thefirst direction; the A/D conversion unit respectively converts the pairsof first analog signals and second analog signals to the pairs of firstdigital signals and second digital signals in parallel along the seconddirection; and the second output unit outputs the digital sum signalsand the second digital signals, obtained as the A/D conversion unitconverts the second analog signals, to the external recipient.

According to a fourth aspect of the present invention, in the imagesensor according to the third aspect, it is preferable that the digitaladder unit adds together the pair of first digital signals output via aswitch that outputs the pair of first digital signals when the pair offirst digital signals and the second digital signal respectivelycorresponding to a first pixel and a second pixel disposed next to eachother are input thereto.

According to a fifth aspect of the present invention, in the imagesensor according to the fourth aspect, it is preferable to furthercomprise: a plurality of signal lines to which the pairs of firstsignals and the second analog signals are individually output from thefirst pixels and the second pixels disposed within the first pixel groupbeing scanned by the scanning unit. Among the plurality of signal lines,a signal line corresponding to one of each pair of first analog signalsalso corresponds to the second analog signal output from the secondpixel in the first pixel group that is scanned by the scanning unitnext.

According to a sixth aspect of the present invention, it the imagesensor according to any one of the third to fifth aspects, it ispreferable that the first output unit and the second output unit share acommon scanning circuit that outputs a scan signal; in response to thescan signal, the first output unit outputs the pairs of first digitalsignals to the external recipient; and in response to the scan signal,the second output unit outputs the digital sum signals and the seconddigital signals to the external recipient.

According to a seventh aspect of the present invention, in the imagesensor according to the sixth aspect, it is preferable that theplurality of pixels, including the first pixels and the second pixels,disposed at the pixel array unit each include a red color filter, agreen color filter or a blue color filter among red color filters, greencolor filters and blue color filters disposed in a Bayer array pattern,and the first pixels have green color filters.

According to an eighth aspect of the present invention, in the imagesensor according to the seventh aspect of the present invention, it ispreferable that the pixel array unit includes a plurality of secondpixel groups each formed with third pixels, each of which receives apair of light fluxes and outputs a pair of third analog signals, and thesecond pixels disposed along the first direction, with the plurality ofsecond pixel groups disposed along the second direction so that a firstpixel group and a second pixel group are set side-by-side at alternatepositions; the first pixels each include a pair of first photoelectricconversion units set side-by-side along the first direction; and thethird pixels each include a pair of third photoelectric conversion unitsset side-by-side along the second direction.

According to a ninth aspect of the present invention, in the imagesensor according to the first aspect, it is preferable to furthercomprise: a first memory in which the pairs of first digital signalsobtained as the A/D conversion unit converts the pairs of first analogsignals are stored; and a second memory in which the digital sum signalseach obtained by adding together, via the digital adder unit, the pairof first digital signals are stored. The first output unit outputs thepairs of first digital signals stored in the first memory to theexternal recipient; and the second output unit outputs the digital sumsignals stored in the second memory to the external recipient.

According to a tenth aspect of the present invention, in the imagesensor according to any one of the third to eighth aspects, it ispreferable to further comprise: a first memory in which the pairs offirst digital signals obtained as the A/D conversion unit converts thepairs of first analog signals are stored; and a second memory in whichthe digital sum signals each obtained by adding together, via thedigital adder unit, the pair of first digital signals and the seconddigital signals obtained as the A/D conversion unit converts the secondanalog signals are stored. The first output unit outputs that pairs offirst digital signals stored in the first memory to the externalrecipient; and the second output unit outputs the digital sum signalsand the second digital signals stored in the second memory to theexternal recipient.

According to an eleventh aspect of the present invention, in the imagesensor according to any one of the second to tenth aspects, it ispreferable that the first pixels each include a micro-lens; and via themicro-lens, a pair of photoelectric conversion units in the first pixeland partial areas ranging in different areas of an exit pupil, throughwhich the pair of light fluxes to be received at the pair ofphotoelectric conversion units in the first pixel pass, achieve aconjugate relation to each other.

According to a twelfth aspect of the present invention, in the imagesensor according to the eleventh aspect, it is preferable that the imagesensor is a backside illumination-type image sensor having a wiringlayer disposed on a side opposite from a side where the micro-lens ispresent relative to the pair of photoelectric conversion units in thefirst pixel.

An image-capturing device according to a thirteenth aspect comprises: animage sensor according to any one of the first to twelfth aspects; afocus detection unit that detects a focusing condition at the opticalsystem by calculating a defocus amount representing an extent of defocusat the optical system through a phase difference detection method basedupon the pairs of first digital signals output through the first outputunit; a focus adjustment unit that adjusts the focusing condition basedupon the defocus amount calculated by the focus detection unit; andimage generation unit that generates image data based upon the digitalsum signals output through the second output unit.

According to a fourteenth aspect of the present invention, in theimage-capturing device according to the thirteenth aspect, it ispreferable that the image generation unit generates the image data basedupon the digital sum signals and the second digital signals outputthrough the second output unit.

An image sensor according to a fifteenth aspect of the present inventioncomprises: pixels, each of which receives a pair of light fluxes andrepeatedly outputs a pair of signals; a first output unit that outputsthe pair of signals to an external recipient each time the pair ofsignals are output from a pixel; an adder unit that generates a sumsignal by adding together the pair of signals each time the pair ofsignals are output from the pixel; and a second output unit thatoutputs, to an external recipient, the sum signal generated each timethe sum signal is generated by the adder unit.

Advantageous Effects of Invention

According to the present invention, an image sensor and animage-capturing device that allow signals for focus detection andsignals for image generation to be read out at high speed can beprovided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 A lateral sectional view showing a digital still camera with aninterchangeable lens, having an image sensor achieved in a firstembodiment installed therein

FIG. 2 An illustration indicating a focus detection position set on thephotographic image plane of the interchangeable lens

FIG. 3 A front view showing the structure of an image sensor in detail

FIG. 4 A front view showing the structure of the image sensor in detail

FIG. 5 An illustration indicating the spectral sensitivitycharacteristics of various color filters

FIG. 6 An illustration showing the structure of a focus detection pixel

FIG. 7 An illustration of focus detection pixels in a sectional view

FIG. 8 An illustration of the structure of a focus detection opticalsystem adopting the split-pupil phase detection method

FIG. 9 A block diagram indicating in detail the relationship between theimage sensor and a body drive control device

FIG. 10 A block diagram showing the structure of the image sensor

FIG. 11 A timing chart of individual read operation for individuallyreading out signals output from the pair of photoelectric conversionunits in each focus detection pixel and sum signal read operation forreading out the sum signal obtained by adding together the signalsoutput from the pair of photoelectric conversion units, executedconcurrently during a single frame period

FIG. 12 A timing chart of individual read operation for individuallyreading out signals output from the pair of photoelectric conversionunits in each focus detection pixel and sum signal read operation forreading out the sum signal obtained by adding together the signalsoutput from the pair of photoelectric conversion units, executedconcurrently during a single frame period

FIG. 13 A flowchart of the processing executed by a CPUa engaged infocus detection operation in a body drive control device in the digitalstill camera

FIG. 14 A flowchart of the processing executed by a CPUb engaged inimage processing operation in the body drive control device in thedigital still camera

FIG. 15 Diagrams indicating correlation operation results obtained inconjunction with a pair of data strings

FIG. 16 A timing chart pertaining to a partial row read

FIG. 17 An illustration showing the structure of a focus detection pixel

FIG. 18 A front view showing the structure of an image sensor in detail

FIG. 19 A block diagram showing the structure of the image sensor

FIG. 20 A front view showing the structure of an image sensor in detail

FIG. 21 A front view showing the structure of an image sensor in detail

FIG. 22 An illustration showing the structure of an image-capturingpixel

FIG. 23 A sectional view of image-capturing pixels

FIG. 24 An illustration of a photographic light flux

FIG. 25 A front view showing the structure of an image sensor in detail

FIG. 26 A block diagram showing the structure of the image sensor

FIG. 27 Illustrations of selection operation at a switch disposed incorrespondence to two adjacent pixel columns

FIG. 28 Illustrations of selection operation at a switch disposed incorrespondence to two adjacent pixel columns

FIG. 29 A timing chart of individual read operation for reading outsignals output from the pair of photoelectric conversion units in eachfocus detection pixel and read operation for reading out an outputsignal equivalent to a signal output from an image-capturing pixel,executed concurrently during a single frame period

FIG. 30 A timing chart pertaining to a partial row read

FIG. 31 A block diagram showing the structure of an image sensor

FIG. 32 Illustrations of selection operation at a switch disposed incorrespondence to two adjacent pixel columns

FIG. 33 A front view showing the structure of an image sensor in detail

FIG. 34 A block diagram showing the structure of the image sensor

FIG. 35 A block diagram showing the structure of an image sensor

FIG. 36 A front view showing the structure of an image sensor in detail

FIG. 37 A front view showing the structure of the image sensor in detail

FIG. 38 A block diagram showing the structure of the image sensor

FIG. 39 A front view showing the structure of an image sensor in detail

FIG. 40 A block diagram showing the structure of the image sensor

FIG. 41 A block diagram showing the structure of an image sensor

DESCRIPTION OF EMBODIMENTS First Embodiment

An image sensor and an image-capturing device achieved in the firstembodiment of the present invention will be described. FIG. 1 shows thestructure of a digital still camera with an interchangeable lens, whichincludes the image sensor in the first embodiment installed therein, ina lateral sectional view. The digital still camera 201 achieved in thefirst embodiment comprises an interchangeable lens 202 and a camera body203. The interchangeable lens 202 among various interchangeable lensesis mounted at the camera body 203 via a mount unit 204.

The interchangeable lens 202 includes a lens 209, a zooming lens 208, afocusing lens 210, an aperture 211 and a lens drive control device 206.The lens drive control device 206 is constituted with a microcomputer, amemory, a drive control circuit and the like (none shown). The lensdrive control device 206 executes drive control for focus adjustment atthe focusing lens 210 and for opening diameter adjustment at theaperture 211, detects the states of the zooming lens 208, the focusinglens 210 and the aperture 211, and engages in communication with a bodydrive control device 214 to be detailed later to transmit lensinformation to the body drive control device 214 and receive camerainformation from the body drive control device 214. The aperture 211forms an opening, the diameter of which can be adjusted, centered on theoptical axis for purposes of light amount adjustment and adjustment ofthe extent of blurring.

An image sensor 212, the body drive control device 214, a liquid crystaldisplay element drive circuit 215, a liquid crystal display element 216,an eyepiece lens 217, a memory card 219 and the like are disposed at thecamera body 203. The image sensor 212 includes pixels, which function asboth image-capturing pixels and focus detection pixels, disposed thereatin a two-dimensional pattern. The image sensor 212 will be described indetail later.

The body drive control device 214 includes a microcomputer, a memory, adrive control circuit and the like. The body drive control device 214 isengaged in repeated execution of drive control for the image sensor 212,read of signals output from the image sensor 212, focus detectionoperation based upon the output signals and focus adjustment for theinterchangeable lens 202. It also executes image processing based uponthe output signals, records the image processing results, controlscamera operations and the like. In addition, the body drive controldevice 214 engages in communication with the lens drive control device206 via an electrical contact point 213 to receive the lens informationand transmit the camera information (indicating a defocus amount, anaperture number and the like).

The liquid crystal display element 216 functions as an electronicviewfinder (EVF). A live view image provided via the image sensor 212 isbrought up on display at the liquid crystal display element 216 by theliquid crystal display element drive circuit 215, and can be observed bythe photographer via the eyepiece lens 217. The memory card 219 is animage storage medium in which images captured at the image sensor 212are stored.

A subject image is formed on the light-receiving surface of the imagesensor 212 with a light flux having passed through the interchangeablelens 202. The subject image undergoes photoelectric conversion at theindividual pixels in the image sensor 212 and signals output from thepixels are transmitted to the body drive control device 214.

The body drive control device 214 calculates the defocus amountindicating the extent of defocus based upon signals output from variouspixels at the image sensor 212 and transmits this defocus amount to thelens drive control device 206. In addition, the body drive controldevice 214 generates image data by processing the output signalsprovided from the individual pixels in the image sensor 212 and storesthe image data thus generated into the memory card 219. It also provideslive view image signals from the image sensor 212 to the liquid crystaldisplay element drive circuit 215 so as to bring up a live view image ondisplay at the liquid crystal display element 216. Moreover, the bodydrive control device 214 provides aperture control information to thelens drive control device 206 to enable control of the opening at theaperture 211.

The lens drive control device 206 updates the lens information incorrespondence to the current focusing state, zooming state and aperturesetting state, the maximum aperture number and the like. Morespecifically, the lens drive control device 206 detects the positions ofthe zooming lens 208 and the focusing lens 210 and the aperture numberset for the aperture 211, and calculates the lens information based uponthe lens positions and the aperture number. Alternatively, it may selectthe lens information corresponding to the lens positions and theaperture number from a lookup table prepared in advance.

The lens drive control device 206 calculates a lens drive quantityindicating the extent to which the lens is to be driven based upon thedefocus amount having been received and drives the focusing lens 210 toa focus match position based upon the lens drive quantity. The lensdrive control device 206 also drives the aperture 211 in correspondenceto the aperture number it has received.

FIG. 2 shows a focus detection position (set through an operation of anoperation member (not shown in FIG. 1) performed by the user) on thephotographic image plane of the interchangeable lens 202. This focusdetection position represents an example of an area (a focus detectionarea, a focus detection position) where an image is sampled on thephotographic image plane when focus detection is executed via a focusdetection pixel group at the image sensor 212, as will be detailedlater. A focus detection area 101 in this example is set at the centerof a rectangular photographic image plane 100. The rectangular focusdetection area 101 extends along the horizontal direction at thephotographic image plane, and output signals from pixels, disposed alonga straight line extending along the longer sides of the focus detectionarea 101, are used for focus detection.

FIGS. 3 and 4 each show in detail the structure of the image sensor 212in a front view of an enlargement of an area near the focus detectionarea 101 on the image sensor 212. FIG. 3 shows the layout of pixels 311(hereafter referred to as focus detection pixels 311), which are used asboth image-capturing pixels and focus detection pixels. The focusdetection pixels 311 are disposed along a row direction (running alongthe horizontal direction) and along a column direction (running alongthe vertical direction) in a dense two-dimensional square grid pattern.FIG. 4 indicates the arrangement with which color filters are disposedat the focus detection pixels 311 in FIG. 3. Color filters, i.e., redcolor filters R, green color filters G and blue color filters B,achieving the spectral sensitivity characteristics indicated in FIG. 5,are disposed at the focus detection pixels 311 in conformance to theBayer array rule.

As FIG. 6 shows, the focus detection pixels 311 each comprise arectangular micro-lens 10 and a pair of photoelectric conversion units13 and 14 formed as splitting two parts separated from each other via anelement separation area 15 ranging along the vertical direction. Thepair of photoelectric conversion units 13 and 14 combined togetherachieve a size equivalent to that of the photoelectric conversion unitof a regular image-capturing pixel. It is to be noted that in order tosimplify the illustration, FIG. 6 does not show any color filter. Inaddition, it is desirable to form the pair of photoelectric conversionunits 13 and 14 as close as possible to each other by minimizing thewidth of the element separation area 15 so as to ensure that the sum ofthe outputs from the pair of photoelectric conversion units 13 and 14 ata focus detection pixel 311 is equivalent to the output of thephotoelectric conversion unit in a regular image-capturing pixel.

FIG. 7 shows focus detection pixels 311 structured as illustrated inFIG. 6 in a sectional view. A light-shielding mask 30 is formed aboveand in close proximity to the photoelectric conversion units 13 and 14,and each pair of photoelectric conversion units 13 and 14 receives lighthaving passed through an opening 30 d in the light-shielding mask 30. Aleveling layer 31 is formed above the light-shielding mask 30 and abovethe leveling layer 31, color filters 38 are formed. A leveling layer 32is formed above the color filters 38 and micro-lenses 10 are formedabove the leveling layer 32. The shapes of the photoelectric conversionunits 13 and 14, defined by the openings 30 d, are projected forward viathe micro-lenses 10 and thus, a pair of focus detection pupils isformed. The photoelectric conversion units 13 and 14 are formed on asemiconductor circuit substrate 29. In addition, the element separationarea 15 is formed in order to separate the photoelectric conversion unit13 from the photoelectric conversion unit 14 in each pair. The structuredescribed above allows the photoelectric conversion units 13 and 14 toeach receive a focus detection light flux in a pair of focus detectionlight fluxes passing through a pair of focus detection pupils in theexit pupil of the interchangeable lens.

FIG. 8 shows the structure of a focus detection optical system used todetect the focusing condition via micro-lenses through the split-pupilphase detection method. It is to be noted that part of a focus detectionpixel group in the focus detection area 101 is shown in an enlargement.An exit pupil 90 in FIG. 8 is set over a distance d along the frontwarddirection from the micro-lenses 10 disposed at the predeterminedimage-forming plane of the interchangeable lens 202 (see FIG. 1). Thedistance d is determined in correspondence to the curvature of themicro-lenses 10, the refractive index of the micro-lenses 10, thedistance between the micro-lenses 10 and the photoelectric conversionunits 13 and 14 and the like, and is referred to as a focus detectionpupil distance in this description. FIG. 11 also shows an optical axis91 of the interchangeable lens, micro-lenses 10, photoelectricconversion units 13 and 14, focus detection pixels 311 and focusdetection light fluxes 73 and 74.

A focus detection pupil 93 is formed as a photoelectric conversion unit13, with the light receiving area thereof defined by an opening 30 d, isprojected via the corresponding micro-lens 10. Likewise, a focusdetection pupil 94 is formed as a photoelectric conversion unit 14, withthe light receiving area thereof defined by the opening 30 d, isprojected via the corresponding micro-lens 10. The focus detectionpupils 93 and 94 take up areas of the exit pupil 90, which are differentfrom each other, are set side-by-side along the horizontal direction,and have shapes achieving line symmetry relative to a vertical linepassing through the optical axis 91.

While FIG. 8 schematically illustrates five consecutive focus detectionpixels 311 present near the photographic optical axis 91 within thefocus detection area 101, the illustration simply provides an example,and the photoelectric conversion units at the other focus detectionpixels 311 located toward the periphery of the image plane also receivelight fluxes arriving at the respective micro-lenses from thecorresponding focus detection pupils 93 and 94. Via the micro-lens 10,the pair of photoelectric conversion units 13 and 14 achieve a conjugaterelation to the partial areas different from each other mentionedearlier, i.e., the pair of focus detection pupils 93 and 94.

The photoelectric conversion unit 13 in a focus detection pixelstructured as described above outputs a signal corresponding to theintensity of an image formed on the micro-lens 10 of the focus detectionpixel 311 with the focus detection light flux 73 having passed throughthe focus detection pupil 93 and having advanced toward the micro-lens10. In addition, the photoelectric conversion unit 14 outputs a signalcorresponding to the intensity of an image formed on the micro-lens 10of the focus detection pixel 311 with the focus detection light flux 74having passed through the focus detection pupil 94 and having advancedtoward the micro-lens 10.

By integrating the outputs from the photoelectric conversion units 13and 14 at the plurality of focus detection pixels 311 disposedside-by-side along the horizontal direction in the focus detection area101 described above, into output groups each corresponding to one of thetwo focus detection pupils 93 and 94, information related to theintensity distribution of a pair of images formed on the array of focusdetection pixels 311 with the focus detection light fluxes 73 and 74passing through the focus detection pupil 93 and the focus detectionpupil 94 is obtained. Image shift detection operation processing(correlation arithmetic processing, phase difference detectionprocessing), to be detailed later, is subsequently executed by using theinformation thus obtained so as to detect an image shift amountrepresenting the extent of image shift manifested by the pair of imagesthrough a method known as the split-pupil phase detection method. Then,by executing a conversion operation on the image shift amount incorrespondence to the proportional relation of the focus detection pupildistance to the interval between the gravitational centers of the pairof focus detection pupils 93 and 94, the deviation (defocus amount) ofthe current image-forming plane (the image-forming plane at the focusdetection position corresponding to the position assumed by themicro-lens array on the predetermined image-forming plane), relative tothe predetermined image-forming plane, is calculated. In more specificterms, the defocus amount (i.e., the deviation of the image-formingplane relative to the predetermined image-forming plane, manifestingalong the direction in which the optical axis 91 extends), is calculatedby multiplying the image shift amount (indicating the extent of imageshift occurring within the plane ranging perpendicular to the opticalaxis 91) by a specific conversion coefficient.

In addition, image signals equivalent to those provided via regularimage-capturing pixels disposed in the Bayer array can be obtained inthe form of output signals generated over the entire image plane andeach representing the sum of the outputs from the photoelectricconversion units 13 and 14 in each focus detection pixel 311.

FIG. 9 is a block diagram showing in detail an aspect of therelationship between the image sensor 212 and the body drive controldevice 214, which is relevant to the present invention. An image sensorcontrol unit 220, a buffer memory 221, a CPUa (microcomputer) 222 and aCPUb (microcomputer) 223 are installed in the body drive control device214. Under control executed by the image sensor control unit 220, theimage sensor 212 controls charge storage (the duration of the chargestorage and the charge storage timing) at the focus detection pixels 311and controls signal output. As will be described later, the image sensor212 executes A/D conversion on signals output from the pairs ofphotoelectric conversion units 13 and 14 in focus detection pixels 311and outputs the A/D conversion results as digital data (focus detectiondata) through a channel 1. At the same time, the image sensor 212outputs digital data (signals equivalent to output signals provided fromregular image-capturing pixels), generated by digitally adding togetherdigital data obtained via the pair of photoelectric conversion units 13and 14 in each focus detection pixel 311, through a channel 2. Thedigital data output through the channel 1 and the channel 2 aretemporarily stored into the buffer memory 221 as digital data for asingle frame. The CPUa 222 executes processing to be described later onthe digital data (focus detection data) corresponding to the pairs ofphotoelectric conversion units 13 and 14 at the focus detection pixels311 in the focus detection area, which have been stored in the buffermemory 221, and thus, executes focus detection. The CPUb 223 displays orrecords an image by executing image processing of the known art on thesingle frame digital data (image data) stored in the buffer memory 221.

As described above, the digital data to be used for purposes of focusdetection and the digital data to undergo image processing are outputfrom the image sensor 212 via different channels with a temporaloverlap. In addition, since the focus detection digital data and theimage generation digital data are processed independently of each otherin the CPU 222 and the CPU 223, the need to temporally separate thefocus detection processing and the image processing from each other iseliminated. In other words, they can be executed simultaneously andindependently of each other.

Next, in reference to FIG. 10, the structure of the image sensor 212,capable of simultaneously outputting, via the two channels, the digitaldata obtained via the pairs of photoelectric conversion units 13 and 14in focus detection pixels 311 and the digital data (signals equivalentto signals output from regular image-capturing pixels) obtained bydigitally adding together the digital data from the pair ofphotoelectric conversion units 13 and 14 in each focus detection pixel311, will be described.

FIG. 10 is a block diagram showing the structure of the image sensor 212(CMOS image sensor). In addition to a pixel array unit 40 achieved bydisposing numerous focus detection pixels 311 each having a pair ofphotoelectric conversion units 13 and 14 in a two-dimensional matrixpattern, the image sensor 212 includes a row scanning circuit 41, acolumn A/D conversion device 42, a second line memory 44, a secondcolumn scanning circuit 51, a second horizontal output circuit 45, acolumn digital adder device 46, a first line memory 48, a first columnscanning circuit 52, a first horizontal output circuit 49 and a timingcontrol circuit 50.

Based upon a master clock input thereto from an external source and acontrol signal input thereto from the image sensor control unit 220, thetiming control circuit 50 in this system configuration generates a clocksignal, control signals and the like, in reference to which the rowscanning circuit 41, the column A/D conversion device 42, the columndigital adder device 46, the first line memory 48, the second linememory 44, the first column scanning circuit 52, the second columnscanning circuit 51 and the like are engaged in operation. The timingcontrol circuit 50 provides the clock signal, the control signals andthe like thus generated to the row scanning circuit 41, the column A/Dconversion device 42, the column digital adder device 46, the first linememory 48, the second line memory 44, the first column scanning circuit52, the second column scanning circuit 51 and the like.

In addition, a drive system for the pixel array unit 40, via which drivecontrol for the individual focus detection pixels 311 is achieved, and asignal processing system for the pixel array unit 40, i.e., the rowscanning circuit 41, the column A/D conversion device 42, the columndigital adder device 46, the first line memory 48, the second linememory 44, the first column scanning circuit 52, the second columnscanning circuit 51, the first horizontal output circuit 49, the secondhorizontal output circuit 45, the timing control circuit 50 and thelike, are integrated onto the chip (semiconductor substrate) on whichthe pixel array unit 40 is formed. Namely, the chip on which thesesystems are integrated is laminated on the chip on which the pixel arrayunit 40 is formed.

Although not shown, the focus detection pixels 311 may assume, forinstance, a 3-transistor structure that includes a transfer transistorthat transfers electric charges resulting from photoelectric conversionexecuted at the pair of photoelectric conversion units 13 and 14 (e.g.,photodiodes) to an FD (floating diffusion) unit, a reset transistor thatcontrols the potential at the FD unit and an amplifier transistor thatoutputs a signal corresponding to the potential at the FD unit inaddition to the photoelectric conversion units 13 and 14, or a4-transistor structure that further includes a selector transistorenabling pixel selection.

At the pixel array unit 40, focus detection pixels 311 aretwo-dimensionally disposed over 2N rows×2M columns. In other words, thepixel array unit 40 includes a focus detection pixel group made up with2M focus detection pixels 311 disposed side-by-side along the horizontaldirection, thus forming a row, and 2N rows of such focus detection pixelgroups are set one next to another along the vertical direction runningperpendicular to the horizontal direction. The focus detection pixel 311in the upper left corner in FIG. 10 is the pixel taking up afirst-row/first-column position, and a green color filter is disposed atthis pixel in conformance to the Bayer array rule. Green color filtersand blue color filters are disposed at the focus detection pixelsforming the first-row pixel group. For this 2N row×2M column pixelarray, a single row control line 21(21(1) through 21(2N)) is wired incorrespondence to each row and two column signal lines ((22 (1)a and22(1)b through 22(2M)a and 22(2M)b) are wired in correspondence to eachcolumn. One end of each row control line 21 (21(1) through 21 (2N))corresponding to a given row is connected to an output end of the rowscanning circuit 41 corresponding to the particular row, and controlsignals R(1) through R(2N) are output to the respective row controllines 21. The row scanning circuit 41, configured with, for instance, ashift register, controls row addresses and row scanning in the pixelarray unit 40 via the row control lines 21(21(1) through 21(2N).

The pairs of photoelectric conversion units 13 and 14 in the variousfocus detection pixels 311 in a given row are connected to the rowscanning circuit 41 through the common row control line 21. In responseto a control signal among the control signals R(1), . . . R(L), . . .R(2N), charge storage control and signal read control for thecorresponding row are executed simultaneously. One of the pair ofphotoelectric conversion units 13 and 14, i.e., the photoelectricconversion unit 13 in each focus detection pixel 311 is connected to oneof the two column signal lines, i.e., the column signal line 22(m)b,installed for the corresponding column. The output signal (analogsignal) from the photoelectric conversion unit 13 is output to thecolumn signal line 22(m)b. The other photoelectric conversion unit 14 inthe pair of photoelectric conversion units 13 and 14 in the focusdetection pixel 311 is connected to the other column signal line 22(m)aof the two column signal lines installed in correspondence to theparticular column. The output signal (analog signal) from thephotoelectric conversion unit 14 is output to the column signal line22(m)a. For instance, assuming that the focus detection pixels 311forming the focus detection pixel group in the Lth row in the pixelarray unit 40 are selected by the control signal R(L) provided from therow scanning circuit 41, the output signals from the pairs ofphotoelectric conversion units 13 and 14 in the focus detection pixels311 in the Lth row are output to the column signal lines (22(1)a and22(1)b through 22(2M)a and 22(2M)b).

The column A/D conversion device 42 includes ADC (analog-digitalconversion) circuits 23(1)a and 23(1)b through 23(2M)a and 23(2M)brespectively disposed in correspondence to the column signal lines22(1)a and 22(1)b through 22(2M)a and 22(2M)b, which are installed incorrespondence to the individual pixel columns in the pixel array unit40. In response to a control signal TA1 provided from the timing controlcircuit 50, the column A/D conversion device 42 converts the pairs ofanalog signals output from the focus detection pixels 311 in the pixelarray unit 40 in correspondence to the individual column positions, toH-bit digital signals and outputs the digital signals resulting from theconversion. “H bits”, indicates a specific number of bits, which may be,for instance, 10 bits, 12 bits or 14 bits.

The second line memory 44 includes memories ((25(1)a and 25(1)b through25(2M)a and 25(2M)b) respectively installed in correspondence to theindividual ADCs ((23(1)a and 23(1)b through 23(2M)a and 23(2M)b)configuring the column A/D conversion device 42. In response to acontrol signal TM2 provided from the timing control circuit 50, thedigital signals output in from the individual ADCs ((23(1)a and 23(1)bthrough 23(2M)a and 23(2M)b) are stored as H-bit digital signals in thesecond line memory 44. In the various memories ((25(1)a and 25(1)bthrough 25(2M)a and 25(2M)b) in the second line memory 44, the outputsignals from the pairs of photoelectric conversion units 13 and 14 inthe single row of focus detection pixels are stored as digital signals.

The column digital adder device 46 includes digital adder circuits(26(1) through 26(2M)) each installed in correspondence to a pair ofADCs among the pairs of ADCs (23(1)a and 23(1)b through 23(2M)a and23(2M)b) configuring the column A/D conversion device 42. In response toa control signal TD1 provided from the timing control circuit 50, thecolumn digital adder device 46 adds together the digital signals outputfrom each pair of ADCs (among 23(1)a and 23(1)b through 23(2M)a and23(2M)b) and outputs the resulting signal as an H-bit digital sumsignal.

The first line memory 48 includes memories (28(1) through 28(2M))respectively installed in correspondence to the digital adder circuits(26(1) through 26(2M)) configuring the column digital adder device 46.In response to a control signal TM1 provided from the timing controlcircuit 50, the digital sum signals each output from one of the digitaladder circuits (26(1) through 26(2M)) are stored into the first linememory 48 as H-bit digital signals. Through this operation, sum signals(equivalent to output signals provided from image-capturing pixels),each obtained by adding together the output signals from the pair ofphotoelectric conversion units 13 and 14 in each focus detection pixelamong the focus detection pixels in a single row, are stored as digitalsignals in the individual memories (28(1) through 28(2M)) in the firstline memory 48.

The second column scanning circuit 51, constituted with, for instance, ashift register, controls the column addresses and column scanning forthe memories (25(1)a and 25(1)b through 25(2M)a and 25(2M)b) in thesecond line memory 44 under control executed by the timing controlcircuit 50. The second line memory 44 is engaged in operation inresponse to a scan signal TS2 provided from the second column scanningcircuit 51. The H-bit digital signals each stored in one of the memories(25(1)a and 25(1)b through 25(2M)a and 25(2M)b) are read out in sequenceinto the second horizontal output circuit 45, and subsequently areserially output to an external recipient as output signals (digitalsignals) provided via the pairs of photoelectric conversion units 13 and14 to be used for purposes of focus detection via the second horizontaloutput circuit 45.

The first column scanning circuit 52, constituted with, for instance, ashift register, controls column addresses and column scanning for thememories (28(1) through 28(2M)) in the first line memory 48 undercontrol executed by the timing control circuit 50. The first line memory48 is engaged in operation in response to a scan signal TS1 providedfrom the first column scanning circuit 52. The H-bit digital sum signalseach stored in one of the memories (28(1) through 28(2M)) are read outin sequence into the first horizontal output circuit 49, andsubsequently are serially output via the first horizontal output circuit49 to an external recipient as output signals (digital signals)equivalent to output signals provided from image-capturing pixels.

Next, in reference to the timing charts presented in FIG. 11 and FIG.12, individual read operation for individually reading out the outputsignals from pairs of photoelectric conversion units in focus detectionpixels and read operation for reading out the sum signals each obtainedby adding together the output signals from the pair of photoelectricconversion units in each focus detection pixel, executed concurrentlyduring a single frame period in the image sensor structured as shown inFIG. 10, will be explained. VS and HS in FIG. 11 and FIG. 12respectively indicate a vertical synchronous signal representing thesingle frame period and a horizontal synchronous signal representing asingle horizontal scan period.

In the operational procedure shown in FIG. 11, control signals R(1),R(2), R(3) through R(2n+1), R(2n+2), R(2n+3) through R(N) are issuedsequentially from the row scanning circuit 41 to the pixel array unit 40in synchronization with the horizontal synchronous signal HS. The analogsignals from the pairs of photoelectric conversion units 13 and 14 inthe focus detection pixels 311 for a single line disposed at a rowcorresponding to one of the control signals R(1), R(2), R(3) throughR(2n+1), R(2n+2), R(2n+3) through R(N), are sequentially output to thecolumn signal lines (22(1)a and 22(1)b through 22(2M)a and 22(2M)b).

FIG. 12 provides an enlarged view of the operation executed in relationto the (2n+1)th row, the (2n+2)th row and the (2n+3)th row in FIG. 11.As the (2n+1)th row in the pixel array unit 40 is selected by thecontrol signal R(2n+1), the analog signals from the pairs ofphotoelectric conversion units 13 and 14 in the focus detection pixels311 for a single line, disposed at the (2n+1)th row, are output to thecolumn signal lines (22(1)a and 22(1)b through 22(2M)a and 22(2M)b). Inresponse to the control signal TA1, the analog signals from the pairs ofphotoelectric conversion units 13 and 14 in the focus detection pixels311 for the single line disposed at the (2n+1)th row, having been outputto the column signal lines (22(1)a and 22(1)b through 22(2M)a and22(2M)b) are respectively converted to digital signals via the ADCs(23(1)a and 23(1)b through 23(2M)a and 23(2M)b) in the column A/Dconversion device 42 connected to the column signal lines (22(1)a and22(1)b through 22(2M)a and 22(2M)b).

In response to the control signal TM2, the digital signals correspondingto the pairs of photoelectric conversion units 13 and 14 in the focusdetection pixels 311 for the single line disposed at the (2n+1)th rowresulting from the digital conversion are stored into the memories(25(1)a and 25(1)b through 25(2M)a and 25(2M)b) respectively in thesecond line memory 44 connected to the ADCs (23(1)a and 23(1)b through23(2M)a and 23(2M)b) in the column A/D conversion device 42.

Concurrently as the digital signals are stored into the second linememory 44, the digital signals resulting from the digital conversionhaving been executed in correspondence to the pairs of photoelectricconversion units 13 and 14 in the focus detection pixels 311 for thesingle line are added together, in response to the control signal TD1.The digital signals corresponding to the pair of photoelectricconversion units 13 and 14 in each of the focus detection pixels 311disposed at the (2n+1)th row are added together via one of the digitaladder circuits (26(1) through 26(2M)) in the column digital adder device46, each installed in correspondence to a specific pair of ADCs amongthe pairs of ADCs (23(1)a and 23(1)b through 23(2M)a and 23(2M)b)configuring the column A/D conversion device 42.

In response to the control signal TM1, the digital sum signalscorresponding to the focus detection pixels 311 for the single linedisposed at the (2n+1)th row, each obtained by adding together theoutput signals from a pair of photoelectric conversion units 13 and 14,are stored into the memories (28(1) through 28(2M)) in the first linememory 48 connected to the digital adder circuits (26(1) through 26(2M))respectively in the column digital adder device 46.

The digital signals corresponding to the pairs of photoelectricconversion units 13 and 14 in the focus detection pixels 311 for thesingle line disposed at the (2n+1)th row, having been stored into thememories (25(1)a and 25(1)b through 25(2M)a and 25(2M)b) in the secondline memory 44, are provided, in response to the scan signal TS2, insequence through a serial output to an external recipient via the secondhorizontal output circuit 45 during the period of time elapsing untilthe next horizontal synchronous signal HS is generated. Based upon thedigital signal output from the second horizontal output circuit 45, thefocus detection CPUa 222 in the body drive control device 214 detectsthe focusing condition at the interchangeable lens 202 (optical system)and adjusts the focusing condition as will be described later inreference to FIG. 13.

Likewise, the digital sum signals corresponding to the focus detectionpixels 311 for the single line disposed at the (2n+1)th row, eachobtained by adding together the output signals from a pair ofphotoelectric conversion units 13 and 14, having been stored into thememories (28(1) through 28(2M)) in the first line memory 48, areprovided in response to the scan signal TS1, in sequence through aserial output to an external recipient via the first horizontal outputcircuit 49 during the period of time elapsing until the next horizontalsynchronous signal HS is generated. Based upon the digital sum signalsoutput from the first horizontal output circuit 49, the image processingCPUb 223 generates image data as will be described later in reference toFIG. 14.

As the control signal R(2n+2) is issued in synchronization with the nexthorizontal synchronous signal HS and the (2n+2)th row in the pixel arrayunit 40 is thus selected, processing is executed for the analog signalsfrom the pairs of photoelectric conversion units 13 and 14 in the focusdetection pixels 311 for a single line disposed at the (2n+2)th row byfollowing a similar operational procedure. Similar processing will berepeatedly executed in response to the control signal R(2n+3) issued insynchronization with the subsequent horizontal synchronous signal HS, aswell.

FIG. 13 and FIG. 14 present flowcharts of operations executed in thedigital still camera (image-capturing device) 201 achieved in the firstembodiment. Processing operations are executed concurrently as indicatedin the flowcharts. FIG. 13 presents a flowchart of the operationexecuted by the focus detection CPUa 222 in the body drive controldevice 214. As power to the digital still camera 201 is turned on instep S100, the body drive control device 214 starts execution of thefocus detection operation in step S110 and subsequent steps. In stepS110, the body drive control device 214 reads out, in framesynchronization, a pair of sets of data provided via the pairs ofphotoelectric conversion units in the focus detection pixels disposedwithin the focus detection area having been selected. The pair of setsof data from the pairs of photoelectric conversion units are constitutedwith the digital signals output through the second horizontal outputcircuit 45, as has been explained earlier. In the following step S120,the body drive control device 214 calculates an image shift amountthrough image shift detection operation processing (correlationarithmetic processing, phase difference detection processing) to bedetailed later based upon the data from the focus detection pixels. Itis to be noted that the position of the focus detection area have beenselected in advance by the photographer via an operation member (notshown).

In step S130, the body drive control device 214 converts the image shiftamount to a defocus amount.

In step S140, the body drive control device 214 makes a decision as towhether or not the current focusing condition at the interchangeablelens 202 (optical system) is close to the focus match state, i.e.,whether or not the absolute value of the defocus amount having beencalculated is equal to or less than a predetermined value. If it isdecided that the current condition is not close to the focus matchstate, the processing proceeds to step S150, in which the body drivecontrol device 214 transmits the defocus amount to the lens drivecontrol device 206 so as to drive the focusing lens 210 in theinterchangeable lens 202 (optical system) to the focus match positionand thus adjust the focusing condition at the interchangeable lens 202.

It is to be noted that the operation also branches to this step if focusdetection cannot be executed. In this case, the body drive controldevice 214 transmits a scan-drive instruction to the lens drive controldevice 206 so as to scan-drive the focusing lens 210 in theinterchangeable lens 202 over the range between infinity and maximumclose-up. The operation then proceeds to step S160.

If, on the other hand, it is decided in step S140 that the currentcondition is close to the focus match state, the processing proceeds tostep S160 in which the body drive control device 214 makes a decision asto whether or not a shutter release has occurred in response to anoperation at a shutter release button (not shown). If it is decided thata shutter release has not occurred, the processing returns to step S110to repeatedly execute the operation described above. If it is decidedthat a shutter release has occurred, the processing proceeds to stepS170 in which the body drive control device 214 waits in standby for thephotographing operation, executed in response to the shutter release, toend, and once the photographing operation ends, the processing returnsto step S110 to repeatedly execute the operation described above.

The image shift detection operation processing (correlation arithmeticprocessing, phase difference detection processing) executed in step S120and step S130 in FIG. 13 will be described in detail. It is to be notedthat the pair of sets of data from the focus detection pixels 311 areobtained discriminately in correspondence to each of the colors in theBayer array.

Since the focus detection pupils 93 and 94 may be vignetted by theaperture opening at the lens, a perfect balance may not be achieved withregard to the amounts of light in the pair of images detected via thefocus detection pixels 311. Accordingly, the body drive control device214 executes a specific type of correlation operation that allows adesired level of image shift detection accuracy to be maintained inspite of the imbalance in the amounts of light. The correlationoperation is executed on a pair of data strings A1 _(n) (A1 ₁, . . . ,A1 _(j): j represents the number of sets of data) and A2 _(n) (A2 ₁, . .. , A2 _(j)) read out from the group of focus detection pixels 311, asexpressed in standardized correlation operation expression (1) of theknown art, applicable in relation to any color, disclosed in JapaneseLaid Open Patent Publication No. 2007-333720, so as to calculate acorrelation quantity C(k).C(k)=Σ|A1_(n) ·A2_(n+1+k) −A2_(n+k) ·A1_(n+1)|  (1)

In expression (1), the Σ operation is cumulatively executed with regardto n. The range assumed for n is limited to the range over which thedata A1 _(n), A1 _(n+1), A2 _(n+k) and A2 _(n+1+k) exist incorrespondence to the image shift amount k. The shift amount k is aninteger that represents a relative shift amount assuming a value takenin units matching the data interval with which the data in the datastrings are sampled. The results of the arithmetic operation executed asexpressed in (1) indicate a minimum value for the correlation quantityC(k) at the shift amount at which the pair of sets of data achieve ahigh level of correlation (when k=kj=2 in FIG. 15(a)), as shown in FIG.15(a). Namely, the correlation quantity C(k) taking a smaller valueindicates a higher level of correlation.

Next, the body drive control device 214 determines the shift amount X,which gives the smallest value C(X) in the continuous correlationquantity graph, by adopting a three-point interpolation method expressedin (2) through (5) below.X=kj+D/SLOP  (2)C(X)=C(kj)−|D|  (3)D={C(kj−1)−C(kj+1)}/2  (4)SLOP=MAX{C(kj+1)−C(kj),C(kj−1)−C(kj)}  (5)

The judgment as to whether or not the shift amount X calculated asexpressed in (2) is reliable is made as follows. As shown in FIG. 15(b),the interpolated minimal value C(X) of the correlation quantityincreases when the level of correlation between the pair of sets of datais low. Accordingly, if C(X) is equal to or greater than a predeterminedthreshold value, the body drive control device 214 judges that the shiftamount is less reliable and cancels the calculated shift amount X.Alternatively, C(X) may be standardized with regard to the datacontrast, and in such a case, if the value obtained by dividing C(X) bySLOP indicating a value in proportion to the contrast is equal to orgreater than a predetermined value, the body drive control device 214judges the calculated shift amount to be not reliable and accordingly,cancels the calculated shift amount X. As a further alternative, if SLOPindicating the value in proportion to the contrast is equal to or lessthan a predetermined value, the subject should be judged to be alow-contrast subject, and accordingly, the body drive control device 214judges the reliability of the calculated shift amount to be low andcancels the calculated shift amount X.

If the level of correlation between the pair of sets of data is low andthe correlation quantity C(X) does not dip at all over the shift rangek_(min) to k_(max), as shown in FIG. 15(c), the minimal value C(X)cannot be determined. In this case, it is decided that focus detectioncannot be executed.

Once the shift amount X, having been calculated, is determined to bereliable, it is converted to an image shift amount shift as expressed in(6) below.shft=PY·X  (6)

PY in expression (6) takes a value twice the pixel pitch with which thefocus detection pixels 311 are disposed (i.e., the pixel pitch withwhich same-color focus detection pixels are disposed).

The body drive control device 214 converts the image shift amount shftcalculated as expressed in (6) to a defocus amount def by multiplyingthe image shift amount by a predetermined conversion coefficient k.def=k·shft1  (7)

The conversion coefficient k in expression (7) takes a value set incorrespondence to the proportional relation of the gravitational centerinterval between the gravitational centers of the pair of focusdetection pupils 93 and 94 to the focus detection pupil distance, whichchanges in correspondence to the aperture F-number at the opticalsystem.

Once three defocus amounts are calculated, each in correspondence to oneof the three colors assumed in the Bayer array, as described above, afinal defocus amount is calculated for the selected focus detection areathrough averaging processing such as simple averaging or weightedaveraging.

FIG. 14 presents a flowchart of the operation executed by the imageprocessing CPUb 223 in the body drive control device 214. As power tothe digital still camera 201 is turned on in step S200, execution of theimage processing operation in step S210 and subsequent steps starts. Instep S210, the CPUb 223 reads out, in frame synchronization, digital sumdata (equivalent to data provided by image-capturing pixels), obtainedby adding together the data output from the pairs of photoelectricconversion units in the focus detection pixels, executes imageprocessing on the data so as to generate a display image and brings upan image display at the electronic viewfinder. The digital sum data readout in step S210 are constituted with the digital sum signals outputfrom the first horizontal output circuit 49 as explained earlier.

In step S220, the CPUb 223 makes a decision as to whether or not ashutter release has occurred in response to an operation of the shutterrelease button (not shown). If it is decided that a shutter release hasnot occurred, the processing returns to step S210 to repeatedly executethe operation described above. If, on the other hand, it is decided thata shutter release has occurred, the processing proceeds to step S230, inwhich the CPUb 223 executes a photographing operation in response to theshutter release. The CPUb 223 first transmits an aperture adjustmentinstruction to the lens drive control device 206 so as to set theaperture number at the interchangeable lens 202 to a control F-number(an F-number selected by the photographer or an automatically setF-number). Once the aperture control is completed, the CPUb 223 readsout the digital sum data (equivalent to data from image-capturing pixelsdisposed in the Bayer array), obtained by adding together the outputdata from the pairs of photoelectric conversion units in the focusdetection pixels. The CPUb 223 generates image data through imageprocessing of the known art (de-mosaic processing, noise processing,gradation processing, white balance processing and the like) executed onthe digital sum data, and stores the image data into the memory card instep S240. Once the sequence of the photographing operation iscompleted, the processing returns to step S210 to repeatedly execute theoperation described above.

In the first embodiment described above, focus detection is executed forthe selected focus detection area only. However, since the focusdetection data for the entire image plane are stored in the buffermemory, focus detection may be executed in correspondence to a pluralityof focus detection areas set anywhere on the image plane and thefocusing condition at the lens may be adjusted based upon the results ofsuch focus detection, provided that the focus detection CPUa 222,assures a high level of processing performance.

In the first embodiment described above, the data obtained by addingtogether the data output from the pairs of photoelectric conversionunits in the focus detection pixels are read in their entirety forpurposes of image generation in correspondence to each frame. However, acircuit system enabling culled read (from selected rows or columns) andpixel sum read (from selected rows or columns), instead of the entiredata read, may be added to the configuration described above and imagedata obtained through such read may be used for purposes of imagedisplay or the like.

In the first embodiment described above, the data from the pairs ofphotoelectric conversion units in all the focus detection pixels usedfor purposes of focus detection are read out in correspondence to eachframe. However, the load of reading out the data from the pairs ofphotoelectric conversion units in all the focus detection pixels issignificant and furthermore, a considerable memory capacity needs to beassured in order to accommodate storage of such data. For this reason,data may be read out as necessary through a frame cull read (data areread out for a single frame out of several frames), through a row cullread (data are read out from one row out of several rows), through apartial row read (data are read out from only some rows), through acolumn cull read (data are read out from one column out of severalcolumns) or through a partial column read (data are read out from onlysome columns).

In the timing chart presented in FIG. 16, which corresponds to FIG. 12,the operation executed in relation to the (2n+1)th row, the (2n+2)th rowand the (2n+3)th row in FIG. 11 for a partial row read (the data fromthe pairs of photoelectric conversion units in the focus detectionpixels in the (2n+2)th row alone are read out) is illustrated in anenlargement.

An operation identical to that in FIG. 12 is executed when the (2n+2)throw in the pixel array unit 40 is selected by the control signalR(2n+2). However, if a row other than the (2n+2)th row is selected (inthe operation executed in response to the control signal R(2n+1) or thecontrol signal R(2n+3) in FIG. 16), no control signal TM is generated.In such a case, the digital signals from the pairs of photoelectricconversion units 13 and 14 in the focus detection pixels 311 for asingle line, resulting from the digital conversion executed at the ADCs((23(1)a and 23(1)b through 23(2M)a and 23(2M)b) in the column A/Dconversion device 42 are not stored into the memories (25(1)a and 25(1)bthrough 25(2M)a and 25(2M)b) in the second line memory 44 connected tothe ADCs ((23(1)a and 23(1)b through 23(2M)a and 23(2M)b) in the columnA/D conversion device 42. In addition, since no scan signal TS2 isgenerated either, data are not sequentially provided through a serialoutput to the external recipient from the second horizontal outputcircuit 45 during the period of time elapsing until the next horizontalsynchronous signal HS is generated.

Rows selected for a partial row read or columns selected for a partialcolumn read can be adjusted based upon information transmitted from thebody drive control device 214 to the image sensor 212 in correspondenceto the position of the selected focus detection area.

The first embodiment described above includes the column A/D conversiondevice 42, which includes ADCs installed therein in a quantitycorresponding to the number of photoelectric conversion units providedin pairs in the focus detection pixels forming each row. In addition,the structure achieved in the first embodiment includes the columndigital adder device 46, which includes digital adder circuits 26, thatdigitally adds together digital output signals from the pairs of ADCs,installed therein in a quantity matching the number of focus detectionpixels forming each row. This configuration enables concurrent executionof the individual read operations for individually reading out theoutput signals from the pairs of photoelectric conversion units in thefocus detection pixels and read operations for reading out the sumsignals (equivalent to signals output from image-capturing pixels) eachobtained by adding together the output signals from a pair ofphotoelectric conversion units during a single frame readout period. Asa result, the problem of the related art, i.e., the need to provide ananalog adder device in correspondence to each focus detection pixel, iseliminated. Namely, the problem of the related art that the individualread operations for individually reading out the output signals from thepairs of photoelectric conversion units in the focus detection pixelsand the read operations for reading out the sum signals (equivalent tooutput signals from image-capturing pixels) each obtained by addingtogether the output signals from a pair of photoelectric conversionunits cannot be executed concurrently during a single frame period isovercome in the image sensor achieved in the embodiment.

The issue in the related art may conceivably be addressed byindividually reading out the output data from the pairs of photoelectricconversion units in all the focus detection pixels at the image sensorduring a single frame period, storing the output data thus read out intoan external buffer memory and executing addition processing on theoutput data from the pairs of photoelectric conversion units having beenstored in the buffer memory. However, this alternative is bound toincrease the processing time for the length of time required for theaddition processing and also increase the external processing load aswell. The structure adopted in the image sensor achieved in theembodiment and the operations executed therein make it possible tohandle the image data read and the image processing in much the same wayas in a standard image sensor. In addition, the image sensor achieved inthe present invention allows only some of the output data from the pairsof photoelectric conversion units in the focus detection pixels to beindividually read out, and in such a case, the load of read processingcan be reduced and furthermore, the buffer memory space allocated fordata storage can be reduced as well.

The problem of the related art may also be addressed by adopting astructure that includes an alternative to the column digital adderdevice 46. For instance, the output data from the pairs of photoelectricconversion units in the focus detection pixels may be horizontallyscanned to provide, in sequence, a serial output via a data holdingmemory (in which data are held with a delay matching the length of timerequired for output of a single set of data), and a digital data addercircuit, both disposed in parallel to the output end of the secondhorizontal output circuit 45, so as to generate sum data by addingtogether the output data from the pair of photoelectric conversion unitsin a focus detection pixel and output the sum data thus generated insynchronization with the output of each individual set of data. However,the data transfer rate will be lowered by an extent matching the lengthof time required for the addition processing (the length of timerequired for addition processing executed in correspondence to eachfocus detection pixel×the total number of focus detection pixels) andthus, high speed data read will not be possible. In the image sensor 212achieved in the embodiment, which includes the column digital adderdevice 46, the addition processing is executed simultaneously incorrespondence to the individual columns independently of one another,and thus, high speed read at a data transfer rate substantially matchingthat achieved at an image sensor constituted with regularimage-capturing pixels alone is enabled.

Second Embodiment

The pair of photoelectric conversion units 13 and 14 in each focusdetection pixel 311 are set side-by-side along the horizontal direction(row direction) in the first embodiment. However, the pair ofphotoelectric conversion units in the focus detection pixel may bedisposed side-by-side along a direction other than the horizontaldirection (row direction) so as to detect an image shift manifestingalong a direction other than the horizontal direction. FIG. 17 shows afocus detection pixel 312 having a structure achieved by rotating thefocus detection pixel 311 in FIG. 6 by 90°. The focus detection pixels312 each comprise a rectangular micro-lens 10 and a pair ofphotoelectric conversion units 16 and 17 formed with two parts separatedfrom each other via an element separation area 18 ranging along thehorizontal direction. The pair of photoelectric conversion units 16 and17 combined together achieve a size equivalent to that of thephotoelectric conversion unit of a regular image-capturing pixel.

FIG. 18, presenting a pixel layout diagram (with a filter array matchingthat in FIG. 4), that corresponds to the pixel layout diagram in FIG. 3,shows in detail the structure of an image sensor 212 having focusdetection pixels 311 and focus detection pixels 312 disposed thereat ina front view. FIG. 18 shows an area near the focus detection area 101 atthe image sensor 212 in an enlarged view. The focus detection pixels 311and the focus detection pixels 312 are disposed in alternate rows.

FIG. 19 is a block diagram showing the structure of the image sensor 212assuming the pixel layout shown in FIG. 18. An explanation given inreference to FIG. 19 will focus on structural features characterizingthe image sensor 212 and an explanation of structural elements identicalto those in FIG. 10 is not provided. The pixel array unit 40 differsfrom that in FIG. 10 in that focus detection pixels 312 each having apair of photoelectric conversion units 16 and 17, separated from eachother along the vertical direction, are disposed in even-numbered rows.

The pairs of photoelectric conversion units 16 and 17 in the focusdetection pixels 312 disposed in an even-numbered row are connected tothe row scanning circuit 41 via a common row control line 21. Inresponse to a control signal R(L) (L is an even number), charge storagecontrol and signal read control are executed simultaneously. One of thepair of photoelectric conversion units 16 and 17, i.e., thephotoelectric conversion units 16 in each focus detection pixel 312disposed in a given even-numbered row, is connected to one of the twocolumn signal lines, i.e., the column signal line 22(m)a, installed forthe corresponding column. The output signal (analog signal) from thephotoelectric conversion unit 16 is output to the column signal line22(m)a. The other photoelectric conversion unit 17 in the pair ofphotoelectric conversion units 16 and 17 in the focus detection pixel312 is connected to the other column signal line 22(m)b of the twocolumn signal lines installed in correspondence to the particularcolumn. The output signal (analog signal) from the photoelectricconversion unit 17 is output to the column signal line 22(m)b. Forinstance, assuming that the focus detection pixels 312 disposed in theLth row in the pixel array unit 40 are selected by the control signalR(L) provided from the row scanning circuit 41, the output signals fromthe pairs of photoelectric conversion units 16 and 17 in the focusdetection pixels 312 in the Lth row are output to the column signallines ((22(1)a and 22(1)b through 22(2M)a and 22(2M)b).

Via the image sensor 212 structured as described above, a phasedifference manifesting with regard to a subject image with a contrastchange occurring along the horizontal direction can be detected basedupon a pair of sets of data obtained by grouping, along the horizontaldirection, the data from the photoelectric conversion units 13 and thedata from the photoelectric conversion units 14 in the pairs ofphotoelectric conversion units 13 and 14 in the focus detection pixels311 corresponding to a single color disposed in an odd-numbered row. Inaddition, a phase difference manifesting with regard to a subject imagewith a contrast change occurring along the vertical direction can bedetected based upon a pair of sets of data obtained by grouping, alongthe vertical direction, the data from the photoelectric conversion units16 and the data from the photoelectric conversion units 17 in the pairsof photoelectric conversion units 16 and 17 in the focus detectionpixels 312 corresponding to a single color disposed in even-numberedrows.

FIG. 20 shows a variation of FIG. 18, with focus detection pixels 311and focus detection pixels 312 disposed in alternate columns. Via theimage sensor 212 adopting such a structure, a phase differencemanifesting with regard to a subject image with a contrast changeoccurring along the horizontal direction can be detected based upon apair of sets of data obtained by grouping, along the horizontaldirection, the data from the photoelectric conversion units 13 and thedata from the photoelectric conversion units 14 in the pairs ofphotoelectric conversion units 13 and 14 in the focus detection pixels311 corresponding to a single color disposed in odd-numbered columns. Inaddition, a phase difference manifesting with regard to a subject imagewith a contrast change occurring along the vertical direction can bedetected based upon a pair of sets of data obtained by grouping, alongthe vertical direction, the data from the photoelectric conversion units16 and the data from the photoelectric conversion units 17 in the pairsof photoelectric conversion units 16 and 17 in the focus detectionpixels 312 corresponding to a single color disposed in an even-numberedcolumn.

FIG. 21 shows a variation of FIG. 18, with focus detection pixels 311and focus detection pixels 312 disposed at alternate positions in astaggered pattern. Namely, focus detection pixels 311 are disposed at“odd-numbered row/odd-numbered column” positions and at “even-numberedrow/even-numbered column” positions, whereas focus detection pixels 312are disposed at “odd-numbered row/even-numbered column” positions and at“even-numbered row/odd-numbered column” positions. Among the colorfilters set in the Bayer array pattern, the green filters are alldisposed at the focus detection pixels 311 and the red color pixels andthe blue color pixels are disposed at the focus detection pixels 312.

Via the image sensor 212 structured as described above, a phasedifference manifesting with regard to a subject image with a contrastchange occurring along the horizontal direction can be detected basedupon a pair of sets of data obtained by grouping, along the horizontaldirection, the data from the photoelectric conversion units 13 and thedata from the photoelectric conversion units 14 in the pairs ofphotoelectric conversion units 13 and 14 in the focus detection pixels311 having disposed thereat green color filters, which assumeodd-numbered row/odd-numbered column positions or even-numberedrow/even-numbered column positions. In addition, a phase differencemanifesting with regard to a subject image with a contrast changeoccurring along the vertical direction can be detected based upon a pairof sets of data obtained by grouping, along the vertical direction, thedata from the photoelectric conversion units 16 and the data from thephotoelectric conversion units 17 in the pairs of photoelectricconversion units 16 and 17 in the focus detection pixels 312 havingdisposed thereat blue color filters, which assume odd-numberedrow/even-numbered column positions or focus detection pixels 312 havingdisposed thereat red color filters, which assume even-numberedrow/odd-numbered column positions.

Third Embodiment

The pixels included in the first embodiment are all focus detectionpixels. However, regular image-capturing pixels each having a single,undivided photoelectric conversion unit and focus detection pixels eachhaving photoelectric conversion units separated from each other may beused in combination so as to reduce the number of focus detection pixelsdisposed at the image sensor as a whole and simplify the overallstructure of the image sensor. In addition, since the number of sets offocus detection data output from the image sensor to an externalrecipient is reduced, the focus detection data can be transferred at adata transfer rate comparable to the data transfer rate at which dataused in image processing are typically transferred.

As FIG. 22 shows, an image-capturing pixel 310 comprises a rectangularmicro-lens 10 and a photoelectric conversion unit 11 with a lightreceiving area thereof restricted by a light-shielding mask, as will bedescribed later.

FIG. 23 shows image-capturing pixels 310 in FIG. 22 in a sectional view.A light-shielding mask 30 is formed above and in close proximity to thephotoelectric conversion units 11 used for image-capturing operation atthe image-capturing pixels 310. The photoelectric conversion units 11each receive light having passed through an opening 30 a in thelight-shielding mask 30. Above the light-shielding mask 30, a levelinglayer 31 is formed and color filters 38 are formed above the levelinglayer 31. Above the color filters 38, a leveling layer 32 is formed andmicro-lenses 10 are formed above the leveling layer 32. The shape ofeach opening 30 a is projected forward via the corresponding micro-lens10. The photoelectric conversion units 11 are formed on a semiconductorcircuit substrate 29.

FIG. 24, which is to be referred to in comparison to FIG. 8, shows aphotographic light flux 71 received at image-capturing pixels 310structured as shown FIG. 22. An explanation of any illustrated itemsidentical to those in FIG. 8 is omitted.

The image-capturing pixels 310 each comprise a micro-lens 10, aphotoelectric conversion unit 11 disposed to the rear of the micro-lensand the like. The shape of an opening 30 a (see FIG. 23) present inclose proximity to the photoelectric conversion unit 11 is projected viathe micro-lens 10 onto the exit pupil 90 set apart by the focusdetection pupil distance d from the micro-lens 10. The shape of theprojected image defines an area 95 that substantially circumscribes thefocus detection pupils 93 and 94.

The photoelectric conversion unit 11 outputs a signal corresponding tothe intensity of an image formed on the micro-lens 11 with aphotographic light flux 71 having passed through the area 95 and havingadvanced toward the micro-lens 10.

FIG. 25 presents a pixel layout diagram (with filters arrayed asillustrated in FIG. 4) that corresponds to the pixel layout diagram inFIG. 3. At the image sensor 212, part of which is shown in FIG. 25,image-capturing pixels 310 and focus detection pixels 311 are disposedat alternate positions in a staggered pattern. Namely, focus detectionpixels 311 are disposed at “odd-numbered row/odd-numbered column”positions and at “even-numbered row/even-numbered column” positions,whereas image-capturing pixels 310 are disposed at “odd-numberedrow/even-numbered column” positions and at “odd-numberedrow/even-numbered column” positions. Among the color filters set in theBayer array pattern, the green color filters are all disposed at thefocus detection pixels 311 and the red color filters and the blue colorfilters are disposed at the image-capturing pixels 310. In order toassure maximum focus detection performance, it is desirable that greencolor filters, demonstrating spectral sensitivity characteristics over arange between those of the spectral sensitivity characteristics of redcolor filters and the spectral sensitivity characteristics of blue colorfilters, as indicated in FIG. 5, be disposed at the focus detectionpixels 311. In addition, due to the presence of the element separationarea 15 at each focus detection pixel 311, the sum of the surface areasof the pair of photoelectric conversion units 13 and 14 at the focusdetection pixel 311 is smaller than the surface area of thephotoelectric conversion unit 11 at an image-capturing pixel 310, asindicated in FIG. 6 and FIG. 22. This means that with respect to theimage-capturing performance, the sum of the photoelectric conversionsignal values output from the pair of photoelectric conversion units 13and 14 at a focus detection pixel 311 is smaller than the photoelectricconversion signal value output from the photoelectric conversion unit 11at an image-capturing pixel 312. For this reason, it is desirable thatthe green color filters, disposed in a greater quantity compared to thered color filters and the blue color filters, be provided at the focusdetection pixels 311.

FIG. 26 is a block diagram showing the structure of the image sensor 212assuming the pixel layout shown in FIG. 25. An explanation given inreference to FIG. 26 will focus on structural features characterizingthe image sensor 212 and an explanation of structural elements identicalto those in FIG. 10 will not be provided. The primary structural featurethat differentiates this structure from that shown in FIG. 10 is asecond column switch device 43 disposed at a position on one side ofwhich the column A/D conversion device 42 is located and on the otherside of which the second line memory 44 and the column digital adderdevice 46 are located. This structure allows both the number of memoriesconfiguring the second line memory 44 and the number of digital addercircuits configuring the column digital adder device 46 to be reduced.

In addition to the pixel array unit 40 with numerous focus detectionpixels 311 each having a pair of photoelectric conversion units 13 and14 disposed in a two-dimensional matrix pattern, the image sensor 212includes the line scanning circuit 41, the column A/D conversion device42, the second column switch device 43, the second line memory 44, thesecond column scanning circuit 51, the second horizontal output circuit45, the column digital adder device 46, a first column switch device 47,the first line memory 48, the first column scanning circuit 52, thefirst horizontal output circuit 49 and the timing control circuit 50.

Based upon a master clock input thereto from an external source and acontrol signal input thereto from the image sensor control unit 220, thetiming control circuit 50 in this system configuration generates a clocksignal, control signals and the like, in reference to which the rowscanning circuit 41, the column A/D conversion device 42, the firstcolumn switch device 47, the second column switch device 43, the columndigital adder device 46, the first line memory 48, the first line memory44, the first column scanning circuit 52, the second column scanningcircuit 51, and the like are engaged in operation. The timing controlcircuit 50 provides the clock signal, the control signals and the likethus generated to the row scanning circuit 41, the column A/D conversiondevice 42, the first column switch device 47, the second column switchdevice 43, the column digital adder device 46, the first line memory 48,the first line memory 44, the first column scanning circuit 52, thesecond column scanning circuit 51 and the like.

At the pixel array unit 40, image-capturing pixels 310 and focusdetection pixels 311 are two-dimensionally disposed over 2N rows×2Mcolumns. The focus detection pixel 311 in the upper left corner in FIG.26 is the pixel taking up a first-row/first-column position, and a greencolor filter is disposed at this pixel in conformance to the Bayer arrayrule. For this 2N row×2M column pixel array, a row control line 21(21(1) through 21(2N)) is wired in correspondence to each row and twocolumn signal lines (22 (1)a and 22(1)b through 22(2M)a and 22(2M)b) arewired in correspondence to each column. A total of 2N row control linesare installed, whereas a total of 4M column signal lines are installed.One end of each row control line 21 (21(1) through 21 (2N))corresponding to a given row is connected to an output end of the rowscanning circuit 41 corresponding to the particular row, and controlsignals R(1) through R(2N) are output to the respective row controllines 21.

The photoelectric conversion units in the image-capturing pixels 310 andthe pairs of photoelectric conversion units 13 and 14 in the variousfocus detection pixels 311 disposed in a given row are connected to therow scanning circuit 41 through the common row control line 21. Inresponse to a control signal R(L), charge storage control and signalread control are executed simultaneously. The photoelectric conversionunit 11 in each image-capturing pixel 310 is connected to one of the twocolumn signal lines installed for the corresponding column, i.e., thecolumn signal line 22(m)a. The signal (analog signal) output from thephotoelectric conversion unit 11 is output to the column signal line22(m)a. One of the pair of photoelectric conversion units 13 and 14,i.e., the photoelectric conversion units 13, in each focus detectionpixel 311 is connected to one of the two column signal lines, i.e., thecolumn signal line 22(m)b, installed for the corresponding column. Theoutput signal (analog signal) from the photoelectric conversion unit 13is output to the column signal line 22(m)b. The other photoelectricconversion unit 14 in the pair of photoelectric conversion units 13 and14 in the focus detection pixel 311 is connected to the other columnsignal line 22(m)a of the two column signal lines installed incorrespondence to the particular column. The output signal (analogsignal) from the photoelectric conversion unit 14 is output to thecolumn signal line 22(m)a. For instance, when the Lth row in the pixelarray unit 40 is selected by the control signal R(L) provided from therow scanning circuit 41, the output signals from the photoelectricconversion units 11 in the image-capturing pixels 310 in the Lth row areoutput to the column signal lines (22(1)a through 22(2M)a) and theoutput signals from the pairs of photoelectric conversion units 13 and14 in the focus detection pixels 311 in the Lth row are output to thecolumn signal lines (22(1)a and 22(1)b through 22(2M)a and 22(2M)b). IfL is an odd-numbered value, the signals on the column signal lines22(2M)b corresponding to the even-numbered columns are invalid signalssince image-capturing pixels 310 are disposed at the even-numberedcolumn positions in this row. In addition, if L is an even-numberedvalue, the signals on the column signal lines 22(2m+1)b corresponding tothe odd-numbered columns are invalid signals since image-capturingpixels 310 are disposed at the odd-numbered column positions in thisrow.

The column A/D conversion device 42 includes 4M ADC (analog-digitalconversion) circuits 23(1)a and 23(1)b through 23(2M)a and 23(2M)brespectively disposed in correspondence to the column signal lines22(1)a and 22(1)b through 22(2M)a and 22(2M)b, which are installed incorrespondence to the individual pixel columns in the pixel array unit40. In response to a control signal TA1 provided from the timing controlcircuit 50, the column A/D conversion device 42 converts analog signalsoutput from the individual pixels in the pixel array unit 40 incorrespondence to the individual columns, to H-bit digital signals(S(1)a and S(1)b through S(2M)a and S(2M)b) and outputs the digitalsignals resulting from the conversion.

The second column switch device 43 includes M switches 24(1, 2) through24(2M−1, 2M), each disposed in correspondence to two successive pixelcolumns. In response to a control signal TW2 provided from the timingcontrol circuit 50, the second column switch device 43 selects digitalsignals each output from one of the ADCs (23(1)a and 23(1)b through23(2M)a and 23(2M)b) and outputs the selected signals.

FIGS. 27(a) and 27(b) illustrate selection operations executed at theswitch 24(2m+1, 2m+2) disposed in correspondence to two successive pixelcolumns (i.e., the (2m+1)th column and the (2m+2)th column). Fourdigital signals S(2m+1)a, S(2m+1)b, S(2m+2)a, S(2m+2)b are input to theswitch 24(2m+1, 2m+2) from the four ADCs 23((2m+1)a, 23(2m+1)b,23(2m+2)a, 23(2m+2)b) corresponding to the two pixel columns (2m+1) and(2m+2). As an alternative, the switch 24(2m+1), (2m+2) may receive, forinstance, 8 (i.e., a multiple of 4) digital signals S(2m+1)a, S(2m+1)b,S(2m+2)a, S(2m+2)b, S(2m+3)a, S(2m+3)b, S(2m+4)a and S(2m+4)b inputthereto from 8 (a multiple of 4) ADCs ((23(2m+1)a, 23(2m+1)b, 23(2m+2)a,23(2m+2)b), 23(2m+3)a, 23(2m+3)b, 23(2m+4)a and 23(2m+4)b correspondingto 4 (a multiple of 2) pixel columns (the (2m+1)th column, the (2m+2)thcolumn), the (2m+3)th column and the (2m+4)th column). In this case, afocus detection pixel 311 is disposed at the (2m+1)th column positionand image-capturing pixels 310 are disposed at the other columnpositions, i.e., the (2m+2)th column position, the (2m+3)th columnposition and the (2m+4)th column position.

FIG. 27(a) illustrates the selection operation executed at the switch24(2m+1, 2m+2) when an odd-numbered row in the pixel array unit 40 isselected via the row scanning circuit 41. In the operation illustratedin FIG. 27(a), four digital signals S(2m+1)a, S(2m+1)b, S(2m+2)a andS(2m+2)b corresponding to the image-capturing pixel 310 disposed at theodd-numbered row/even-numbered column position and the focus detectionpixel 311 disposed at the odd-numbered row/odd-numbered column positionare input to the switch 24(2m+1, 2m+2). The signal S(2m+2)b among thesesignals is an invalid signal.

In response to the control signal TW2 (identification informationindicating an odd-numbered row or an even-numbered row) input to thesecond column switch device 43, the switch 24(2m+1, 2m+2) selects thedigital signals S(2m+1)a and S(2m+1)b corresponding to the pair ofphotoelectric conversion units in the focus detection pixel 311 as apair of signals (Q(2m+1, 2m+2)a and Q(2m+1, 2m+2)b) to undergo digitaladdition and outputs the selected digital signals.

FIG. 27(b) illustrates the selection operation executed at the switch24(2m+1, 2m+2) when an even-numbered row in the pixel array unit 40 isselected via the row scanning circuit 41. Four digital signals S(2m+1)a,S(2m+1)b, S(2m+2)a and S(2m+2)b corresponding to the image-capturingpixel 310 disposed at the even-numbered row/odd-numbered column positionand the focus detection pixel 311 disposed at the even-numberedrow/even-numbered column position are input to the switch 24(2m+1,2m+2). The signal S(2m+1)b among these signals is an invalid signal.

In response to the control signal TW2 (identification informationindicating an odd-numbered row or an even-numbered row) input to thesecond column switch device 43, the switch 24(2m+1, 2m+2) selects thedigital signals S(2m+2)a and S(2m+2)b corresponding to the pair ofphotoelectric conversion units 13, 14 in the focus detection pixel 311as a pair of signals (Q(2m+1, 2m+2)a and Q(2m+1, 2m+2)b) correspondingto the pair of photoelectric conversion units 13 and 14 in the focusdetection pixel 311, and outputs the selected digital signals.

The second line memory 44 includes a total of 2M memories (25(1, 2)a and25(1, 2)b through 25(2M−1, 2M)a and 25(2M−1, 2M)b) installed in pairs,each pair corresponding to one of the M switches 24(1, 2) through24(2M−1, 2M) in the second column switch device 43. In response to acontrol signal TM2 provided from the timing control circuit 50, eachpair of digital signals among pairs of digital signals (Q (1, 2)a and Q(1, 2)b through Q(2M−1, 2M)a and Q(2M−1, 2M)b) corresponding to thepairs of focus detection units 13 and 14 in the focus detection pixels311, output via one of the M switches 24(1, 2) through 24(2M−1, 2M), arestored as H-bit digital signals into the second line memory 44. Throughthis operation, the output signals from the pairs of photoelectricconversion units 13 and 14 in the M focus detection pixels disposed in asingle row are stored as digital signals in the individual memories (25(1, 2)a and 25(1, 2)b through 25(22M−1, 2M)a and 25(22M−1, 2M)b)configuring the second line memory 44.

The column digital adder device 46 includes a total of M digital addercircuits (26(1, 2) through 26(2M−1, 2M)) respectively disposed incorrespondence to the M switches 24(1, 2) through 24(2M−1, 2M) in thesecond column switch device 43. In response to a control signal TD1provided from the timing control circuit 50, the column digital adderdevice 46 adds together the signals in each pair of digital signalsamong the pairs of digital signals (Q (1, 2)a and Q (1, 2)b throughQ(2M−1, 2M)a and Q(2M−1, 2M)b) corresponding to the pairs ofphotoelectric conversion units 13 and 14 in the focus detection pixels311 respectively output via the M switches 24(1, 2) through 24(2M−1,2M), and outputs the results as H-bit digital sum signals (P(1, 2)through P(2M−1, 2M)).

The first column switch device 47 includes M switches 27(1, 2) through27(2M−1, 2M), each disposed in correspondence to two successive pixelcolumns. In response to a control signal TW1 (identification informationindicating an odd-numbered row or an even-numbered row) provided fromthe timing control circuit 50, the first column switch device 47 selectsdigital signals among the digital signal (S(1)a and S(2)a through2(2M−1)a and S(2M)a) respectively output via the 2M ADCs (23(1)a through23 (2M)a) and the digital sum signals (P (1, 2) through P (2M−1, 2M))output respectively via the M digital adder circuits (26(1, 2) through26(2M−1, 2M)) and outputs the selected signals.

FIGS. 28(a) and 28(b) illustrate selection operations executed at theswitch 27(2m+1, 2m+2) disposed in correspondence to two successive pixelcolumns (i.e., the (2m+1)th column and the (2m+2)th column). Two digitalsignals S(2m+1)a and S(2m+2)a are input to the switch 27(2m+1, 2m+2)from the two ADCs (23(2m+1)a and 23(2m+2)a) corresponding to two pixelcolumns (2m+1) and (2m+2) and also a single digital sum signal P(2m+1,2m+2) is input to the switch 27(2m+1, 2m+2) from the digital addercircuit 26(2m+1, 2m+2).

FIG. 28(a) illustrates the selection operation executed at the switch27(2m+1, 2m+2) when an odd-numbered row in the pixel array unit 40 isselected via the row scanning circuit 41. In the operation executed asillustrated in FIG. 28(a), a single digital signal S(2m+2)acorresponding to the photoelectric conversion unit 11 in theimage-capturing pixel 310 disposed at the odd-numbered row/even-numberedcolumn position, a single digital signal S(2m+1)a corresponding to thephotoelectric conversion unit 14 in the focus detection pixel 311disposed at the odd-numbered row/odd-numbered column position, and thedigital sum signal P(2m+1, 2m+2) (equivalent to a signal output from animage-capturing pixel) obtained by adding together the pair of signalsS(2m+1)a and S(2m+1)b corresponding to the pair of photoelectricconversion units 13 and 14 in the focus detection pixel 311 disposed atthe odd-numbered row/odd-numbered column position, provided via thedigital adder circuit 26(2m+1, 2m+2), are input to the switch 27(2m+1,2m+2). Among these signals, the signal S(2m+1)a input from the ADC23(2m+1)a is not equivalent to a signal output from an image-capturingpixel.

In response to the control signal TW1 (identification informationindicating an odd-numbered row or an even-numbered row) input to thefirst column switch device 47, the switch 27(2m+1, 2m+2) selects thedigital sum signal P(2m+1, 2m+2) obtained by adding together the digitalsignals corresponding to the pair of photoelectric conversion units inthe focus detection pixel 311 and outputs the selected digital sumsignal as a signal U(2m+1) equivalent to an image-capturing pixel signalthat would be output from a virtual image-capturing pixel disposed atthe odd-numbered column position. The switch 27 (2m+1, 2m+2) alsoselects the digital signal S(2m+2)a corresponding to the image-capturingpixel 310 and outputs the selected signal as a signal U(2m+1) from theimage-capturing pixel disposed at the even-numbered column position.

FIG. 28(b) illustrates the selection operation executed at the switch27(2m+1, 2m+2) when an even-numbered row in the pixel array unit 40 isselected via the row scanning circuit 41. A single digital signalS(2m+1)a corresponding to the photoelectric conversion unit 11 in theimage-capturing pixel 310 disposed at the even-numbered row/odd-numberedcolumn position, a single digital signal S(2m+2)a corresponding to thephotoelectric conversion unit 14 in the focus detection pixel 311disposed at the even-numbered row/even-numbered column position, and thedigital sum signal P(2m+1, 2m+2) (equivalent to a signal output from animage-capturing pixel) obtained by adding together the pair of signalsS(2m+2)a and S(2m+2)b corresponding to the pair of photoelectricconversion units 13 and 14 in the focus detection pixel 311 disposed atthe even-numbered row/even-numbered column position, provided via thedigital adder circuit 26(2m+1, 2m+2) are input to the switch 27(2m+1,2m+2). Among these signals, the signal S(2m+2)a is not equivalent to asignal output from an image-capturing pixel.

In response to the control signal TW1 (identification informationindicating an odd-numbered row or an even-numbered row) input to thefirst column switch device 47, the switch 27(2m+1, 2m+2) selects thedigital sum signal P(2m+1, 2m+2) obtained by adding together the digitalsignals corresponding to the pair of photoelectric conversion units inthe focus detection pixel 311 and outputs the selected digital sumsignal as a signal U(2m+2) equivalent to an image-capturing pixel signalthat would be output from a virtual image-capturing pixel disposed atthe even-numbered column position and also selects the digital signalS(2m+1)a corresponding to the image-capturing pixel 310 and outputs theselected signal as a signal U(2m+1) from the image-capturing pixeldisposed at the odd-numbered column position.

The first line memory 48 includes a total of 2M memories (28(1) through28(2M)) installed in pairs, with each pair corresponding to one of the Mswitches (27(1, 2) through 27(2M−1, 2M)) in the column switch device 47.In response to the control signal TM1 provided from the timing controlcircuit 50, each pair of digital signals output via one of the switches(27(1, 2) through 27(2M−1, 2M)) are stored as H-bit digital signals intothe first line memory 48. Through this operation, in the individualmemories (28(1) through 28(2M)) configuring the first line memory 48,the sum signals (equivalent to output signals from image-capturingpixels) each obtained by adding together the output signals from thepair of photoelectric conversion units 13 and 14 in one of the focusdetection pixels in a single row, and the signals output from thephotoelectric conversion units in the image-capturing pixels disposed inthe row are stored as digital signals in a sequence corresponding to theorder with which the focus detection pixels and the image-capturingpixels are disposed in the row.

The second column scanning circuit 51, constituted with, for instance, ashift register, controls column addresses and column scanning for thememories (25(1)a and 25(1)b through 25(2M)a and 25(2M)b) in the secondline memory 44 under control executed by the timing control circuit 50.The second line memory 44 is engaged in operation in response to a scansignal TS2 provided from the second column scanning circuit 51. Theindividual H-bit digital signals stored in the memories (25(1, 2)a and25(1, 2)b through 25(2M−1, 2M)a and 25(2M−1, 2M)b) are read out insequence into the second horizontal output circuit 45, and subsequentlyare serially output (as 2M sets of data) to an external recipient asoutput signals (digital signals) provided via the pairs of photoelectricconversion units 13 and 14 to be used for purposes of focus detectionvia the second horizontal output circuit 45.

The first column scanning circuit 52, constituted with, for instance, ashift register, controls column addresses and column scanning for thememories (28(1) through 28(2M)) in the first line memory 48 undercontrol executed by the timing control circuit 50. The first line memory48 is engaged in operation in response to a scan signal TS1 providedfrom the first column scanning circuit 52. The individual H-bit digitalsignals and digital sum signals stored in the memories (28(1) through28(2M)) are read out in sequence into the first horizontal outputcircuit 49, and subsequently are serially output, via the firsthorizontal output circuit 49, to an external recipient as output signals(digital signals) equivalent to output signals provided fromimage-capturing pixels.

Next, in reference to the timing chart presented in FIG. 29, individualread operation for individually reading out the output signals (signalsused for focus detection) from the pairs of photoelectric conversionunits in the focus detection pixels and read operation for reading outthe output signals (signals to undergo image processing) equivalent tooutput signals from image-capturing pixels, executed concurrently duringa single frame period in the image sensor structured as shown in FIG.26, will be explained.

The row scanning selection operation executed via the row scanningcircuit 41 in the image sensor structured as shown in FIG. 26 isessentially identical to that explained in reference to FIG. 11.

FIG. 29 provides an enlarged view of the operation executed in relationto the (2n+1)th row, the (2n+2)th row and the (2n+3)th row in FIG. 11.As the (2n+1)th row in the pixel array unit 40 is selected by thecontrol signal R(2n+1), the analog signals for a single line from thefocus detection pixels 311 and the image-capturing pixels 310, disposedin the (2n+1)th row are output to the column signal lines (22(1)a and22(1)b through 22(2M)a and 22(2M)b). In response to the control signalTA1, the analog signals for the single line from the pairs ofphotoelectric conversion units 13 and 14 in the focus detection pixels311 and from the photoelectric conversion units 11 in theimage-capturing pixels 310, respectively disposed at the odd-numberedcolumn positions and the even-numbered column positions in the (2n+1)throw, having been output to the column signal lines (22(1)a and 22(1)bthrough 22(2M)a and 22(2M)b) are individually converted to digitalsignals via the ADCs (23(1)a and 23(1)b through 23(2M)a and 23 (2M)b) inthe column A/D conversion device 42 connected to the column signal lines22(1)a and 22(1)b through 22(2M)a and 22(2M)b respectively.

In response to the control signal TW2, the digital signals correspondingto the pairs of photoelectric conversion units 13 and 14 in the focusdetection pixels 311 disposed at the odd-numbered column positions,among the digital signals for a single line from the pairs ofphotoelectric conversion units 13 and 14 in the focus detection pixels311 disposed at the odd-numbered column positions and theimage-capturing pixels 310 disposed at the even numbered columnpositions in the (2n+1)th row, which are input from the column A/Dconversion device 42 to the second column switch device 43, are selectedvia the second column switch device 43 (24(1, 2) through 24(2M−1, 2M))and the digital signals thus selected are output.

In response to the control signal TM2, the digital signals correspondingto the pairs of photoelectric conversion units 13 and 14 in the focusdetection pixels 311 disposed at the odd-numbered column positions,output from the second column switch device 43 (24(1, 2) through24(2M−1, 2M)) are stored into the 2M memories (25(1, 2)a, and 25(1, 2)bthrough 25(2M−1, 2M)a and 25(2M−1, 2M)b) in the second line memory 44.

Concurrently as the operation described above is executed, the digitalsignals corresponding to the pair of photoelectric conversion units 13and 14 in each of the focus detection pixels 311 disposed at theodd-numbered column positions are added together via one of the Mdigital adder circuits (26(1, 2) through 26(2M−1, 2M)) in the columndigital adder device 46 in response to the control signal TD1 and theresulting sum signal is then output.

In response to the control signal TW1, the first column switch device 47(27(1, 2) through 27(2M−1, 2M)) selects the digital sum signals eachobtained by adding together the digital signals corresponding to thepair of photoelectric conversion units 13 and 14 in one of the focusdetection pixels 311 disposed at the odd-numbered column positions andthe digital signals corresponding to the photoelectric conversion units11 in the image-capturing pixels 310 disposed at the even-numberedcolumn positions, among the digital signals input to the first columnswitch device 47, i.e., the digital signals corresponding to thephotoelectric conversion units 14 in the pairs of photoelectricconversion units in the focus detection pixels 311 disposed at theodd-numbered column positions, the digital signals corresponding to thephotoelectric conversion units 11 in the image-capturing signals 310disposed at the even-numbered column positions and the digital sumsignals each obtained by adding together the digital signalscorresponding to the pair of photoelectric conversion units 13 and 14 inone of the focus detection pixels 311 disposed at the odd-numberedcolumn positions. The digital sum signals obtained by adding togetherthe digital signals from the pairs of photoelectric conversion units 13and 14 in the focus detection pixels 311 disposed at the odd-numberedcolumn positions are output as signals that would be output fromimage-capturing pixels disposed at the odd-numbered column positions,whereas the digital signals from the photoelectric conversion units 11in the image-capturing signals 310 disposed at the even-numbered columnpositions are output as signals from the image-capturing pixels disposedat the even-numbered column positions.

In response to the control signal TM1, the digital sum signals obtainedby adding together the digital signals from the pairs of photoelectricconversion units 13 and 14 in the focus detection pixels 311 disposed atthe odd-numbered column positions and the digital signals from thephotoelectric conversion units 11 in the image-capturing signals 310disposed at the even-numbered column positions, having been selected andoutput by the first column switch device 47, are stored into thememories (28(1) through 28(2M)) in the first line memory 48.

In response to the scan signal TS2, the digital signals corresponding tothe pairs of photoelectric conversion units 13 and 14 in the M focusdetection pixels 311 disposed at the odd-numbered column positions inthe (2n+1)th row, having been stored into the 2M memories (25(1, 2)a and25(1, 2)b through 25(2M−1, 2M)a and 25(2M−1, 2M)b) in the second linememory 44, are provided in sequence to an external recipient through aserial output from the second horizontal output circuit 45 over theperiod of time elapsing until the next horizontal synchronous signal HSis generated.

Likewise, in response to the scan signal TS1, the 2M digital signalsequivalent to image-capturing pixel output signals for the (2n+1)th row(the digital sum signals obtained by adding together the digital signalsfrom the pairs of photoelectric conversion units 13 and 14 in the focusdetection pixels 311 disposed at the odd-numbered column positions andthe digital signals from the photoelectric conversion units 11 in theimage-capturing pixels 310 disposed at the even-numbered columnpositions), having been stored into the memories (28(1) through 28(2M))in the first line memory 48, are sequentially provided to an externalrecipient through a serial output from the first horizontal outputcircuit 49 during the period of time elapsing until the next horizontalsynchronous signal HS is generated.

As the control signal R(2n+2) is provided in synchronization with thenext horizontal synchronous signal HS, and the (2n+2)th row in the pixelarray unit 40 is selected, the analog signals for a single line areoutput from the focus detection pixels 311 and the image-capturingpixels 310 disposed in the (2n+2)th row to the column signal lines(22(1)a and 22(1)b through 22(2M)a and 22(2M)b). In response to thecontrol signal TA1, the analog signals for a single line from the pairsof photoelectric conversion units 13 and 14 in the focus detectionpixels 311 at the even-numbered column positions and from thephotoelectric conversion units 11 in the image-capturing pixels 310 atthe odd-numbered column positions in the (2n+2)th row having been outputto the column signal lines (22(1)a and 22(1)b through 22(2M)a and22(2M)b) are converted to digital signals via the ADCs (23(1)a and23(1)b through 23(2M)a and 23(2M)b) in the column A/D conversion device42 connected to the column signal lines (22(1)a and 22(1)b through22(2M)a and 22(2M)b) respectively.

In response to the control signal TW2, the digital signals correspondingto the pairs of photoelectric conversion units 13 and 14 in the focusdetection pixels 311 disposed at the even-numbered column positions,among the digital signals for a single line from the pairs ofphotoelectric conversion units 13 and 14 in the focus detection pixels311 disposed at the even-numbered column positions and the photoelectricconversion units 11 in the image-capturing pixels 310 disposed at theodd-numbered column positions in the (2n+2)th row, which are input fromthe column A/D conversion device 42 to the second column switch device43, are selected via the second column switch 43 (24(1, 2) through24(2M−1, 2M)) and the digital signals thus selected are output.

In response to the control signal TM2, the digital signals correspondingto the pairs of photoelectric conversion units 13 and 14 in the focusdetection pixels 311 disposed at the even-numbered column positions,output from the second column switch device 43 (24(1, 2) through24(2M−1, 2M)) are stored into the 2M memories (25(1, 2)a, and 25(1, 2)bthrough 25(2M−1, 2M)a and 25(2M−1, 2M)b) in the second line memory 44.

Concurrently as the operation described above is executed, the digitalsignals corresponding to the pair of photoelectric conversion units 13and 14 in each of the focus detection pixels 311 disposed at theeven-numbered column positions are added together via one of the Mdigital adder circuits (26(1, 2) through 26(2M−1, 2M)) in the columndigital adder device 46 in response to the control signal TD1 and theresulting sum signal is then output.

In response to the control signal TW1, the first column switch device 47(27(1, 2) through 27(2M−1, 2M)) selects the digital sum signals eachobtained by adding together the digital signals corresponding to thepair of photoelectric conversion units 13 and 14 in one of the focusdetection pixels 311 disposed at the even-numbered column positions andthe digital signals corresponding to the photoelectric conversion units11 in the image-capturing pixels 310 disposed at the odd-numbered columnpositions, among the digital signals input to the first column switchdevice 47, i.e., the digital signals corresponding to the photoelectricconversion units 14 in the pairs of photoelectric conversion units inthe focus detection pixels 311 disposed at the even-numbered columnpositions, the digital signals corresponding to the photoelectricconversion units 11 in the image-capturing signals 310 disposed at theodd-numbered column positions and the digital sum signals each obtainedby adding together the digital signals corresponding to the pair ofphotoelectric conversion units 13 and 14 in one of the focus detectionpixels 311 disposed at the even-numbered column positions. The digitalsum signals obtained by adding together the digital signals from thepairs of photoelectric conversion units 13 and 14 in the focus detectionpixels 311 disposed at the even-numbered column positions are output assignals that would be output from image-capturing pixels disposed at theeven-numbered column positions, whereas the digital signals from thephotoelectric conversion units 11 in the image-capturing signals 310disposed at the odd-numbered column positions are output as signals fromthe image-capturing pixels disposed at the odd-numbered columnpositions.

In response to the control signal TM1, the digital sum signals obtainedby adding together the digital signals from the pairs of photoelectricconversion units 13 and 14 in the focus detection pixels 311 disposed atthe even-numbered column positions and the digital signals from thephotoelectric conversion units 11 in the image-capturing signals 310disposed at the odd-numbered column positions, having been selected andoutput by the first column switch device 47, are stored into thememories (28(1) through 28(2M)) in the first line memory 48.

In response to the scan signal TS2, the digital signals corresponding tothe pairs of photoelectric conversion units 13 and 14 in the M focusdetection pixels 311 disposed at the even-numbered column positions inthe (2n+2)th row, having been stored into the 2M memories (25(1, 2)a and25(1, 2)b through 25(2M−1, 2M)a and 25(2M−1, 2M)b) in the second linememory 44, are provided in sequence to an external recipient through aserial output from the second horizontal output circuit 45 over theperiod of time elapsing until the next horizontal synchronous signal HSis generated. Based upon the digital signals output through the secondhorizontal output circuit 45, the focus detection CPUa 222 in the bodydrive control device 214 detects the focusing condition at theinterchangeable lens 202 (optical system) and adjusts the focusingcondition as indicated in FIG. 13.

Likewise, in response to the scan signal TS1, the 2M digital signalsequivalent to image-capturing pixel output signals for the (2n+2)th row(the digital sum signals obtained by adding together the digital signalsfrom the pairs of photoelectric conversion units 13 and 14 in the focusdetection pixels 311 disposed at the even-numbered column positions andthe digital signals from the photoelectric conversion units 11 in theimage-capturing pixels 310 disposed at the odd-numbered columnpositions), having been stored into the memories (28(1) through 28(2M))in the first line memory 48, are sequentially provided to an externalrecipient through a serial output from the first horizontal outputcircuit 49 during the period of time elapsing until the next horizontalsynchronous signal HS is generated. Based upon the 2M digital signals(the digital sum signals obtained by adding together the digital signalscorresponding to the pairs of photoelectric conversion units 13 and 14in the focus detection pixels 311 disposed at the even-numbered columnpositions and the digital signals corresponding to the photoelectricconversion units 11 in the image-capturing pixels 310 disposed at theodd-numbered column positions) output through the first horizontaloutput circuit 49, the image processing CPUb 223 in the body drivecontrol device 214 generates image data as indicated in FIG. 14.However, in the processing executed in this embodiment in step S210 inFIG. 14, the data carried in the 2M digital signals (the digital sumsignals obtained by adding together the digital signals corresponding tothe pairs of photoelectric conversion units 13 and 14 in the focusdetection pixels 311 disposed at the even-numbered column positions andthe digital signals corresponding to the photoelectric conversion units11 in the image-capturing pixels 310 disposed at the odd-numbered columnpositions) having been output through the first horizontal outputcircuit 49 are read out, the data thus read out undergo display imageprocessing and then an image display is brought up at the electronicviewfinder. In addition, in step S230 in FIG. 14, the data carried inthe 2M digital signals (the digital sum signals obtained by addingtogether the digital signals corresponding to the pairs of photoelectricconversion units 13 and 14 in the focus detection pixels 311 disposed atthe even-numbered column positions and the digital signals correspondingto the photoelectric conversion units 11 in the image-capturing pixels310 disposed at the odd-numbered column positions), having been outputthrough the first horizontal output circuit 49, are read out, the datathus read out undergo image processing of the known art (de-mosaicprocessing, noise processing, gradation processing, white balanceprocessing and the like) and image data are thus generated.

As the control signal R(2n+3) is issued in synchronization with the nexthorizontal synchronous signal HS and the (2n+3)th row in the pixel arrayunit 40 is selected, processing is repeatedly executed for the focusdetection pixels 311 and the image-capturing pixels 310 in the (2n+3)throw accounting for another line through an operational procedure similarto that followed in conjunction with the control signal R(2n+1).

In the third embodiment described above, the image-capturing pixels 310and the focus detection pixels 311 are disposed in combination at thepixel array unit 40, with the focus detection pixels 311 set atpositions taken by the green filters in the Bayer array and theimage-capturing pixels 310 set at positions taken by the red colorfilters and the blue color filters in the Bayer array. In addition, theselection processing executed at the first column switch device 47 andthe second column switch device 43 is switched depending upon whether anodd-numbered row or an even-numbered row in the pixel array unit 40 hasbeen scanned by the row scanning circuit 41. This system makes itpossible to simplify the structure of the image sensor in the currentembodiment compared to the structure adopted for the image sensor shownin FIG. 10. In more specific terms, the quantity of digital circuitsconfiguring the column digital adder circuit 46, which are bound to takeon a greater circuit scale compared to that of switch circuits, can bereduced (from 2M to M digital circuits). Likewise, the quantity ofmemories configuring the second line memory 44, which are bound to takeon a greater circuit scale compared to that of switch circuits, can bereduced (from 4M to 2M memories). In addition, the number of sets ofdata output through the second horizontal output circuit 45 during ahorizontal scan period is halved from 4M to 2M in comparison to thecorresponding number of sets of data output at the image sensor shown inFIG. 10. With the number of sets of data output through the secondhorizontal output circuit 45 during the horizontal scan period reducedto equal the number of sets of data output through the first horizontaloutput circuit 49 during the horizontal scan period, the overall datatransfer rate can be lowered. In addition, since the focus detectiondata read out from the second horizontal output circuit 45 areexclusively data originating from the focus detection pixels havingdisposed therein green filters, the focus detection operation is betterfacilitated (a great many subjects in natural environments assume agreen color contrast and also, the focus position corresponding to greencolor is normally designated as the focus match position in conjunctionwith a photographic lens manifesting chromatic aberration).

In the third embodiment described above, the number of sets of focusdetection data output as a result of horizontal scanning of a given row,executed via the second column scanning circuit 51, and the number ofsets of image processing data output as a result of horizontal scanningof the row executed via the first column scanning circuit 52, match eachother. This means that the structure of the image sensor may be evenfurther simplified through functional commonality of the second columnscanning circuit 51 and the first column scanning circuit 52 by, forinstance, using the scan signal TS1 for the first column scanningcircuit 52 also as the scan signal TS2 for the second line memory 44. Anexample of an image sensor that only includes the first column scanningcircuit 52 and dispenses with the second column scanning circuit 51,which is made possible through the use of the scan signal TS1 for thefirst column scanning circuit also as the scan signal TS2 for the secondline memory 44, is presented in FIG. 41.

In the third embodiment described above, the data from the pairs ofphotoelectric conversion units in all the focus detection pixels areread out for purposes of focus detection in correspondence to eachframe. However, the load of reading out the data from the pairs ofphotoelectric conversion units in all the focus detection pixels issignificant and furthermore, considerable memory capacity needs to beassured in order to accommodate storage of such data. For this reason,data may be read out as necessary through a frame cull read (data areread out for a single frame out of several frames), through a row cullread (data are read out from one row out of several rows), through apartial row read (data are read out from only some rows), through acolumn cull read (data are read out from one column out of severalcolumns) or through a partial column read (data are read out from onlysome columns).

In reference to the timing chart presented in FIG. 30, which correspondsto FIG. 29, the operation executed for a partial row read (the data fromthe pairs of photoelectric conversion units in the focus detectionpixels in the (2n+2)th row alone are read out) will be described. Anoperation identical to that in FIG. 29 is executed when the (2n+2)th rowin the pixel array unit 40 is selected by the control signal R(2n+2).However, if a row other than the (2n+2)th row is selected (in theoperation executed in response to the control signal R(2n+1) or thecontrol signal R(2n+3) in FIG. 30), no control signal TM2 is generated,and data corresponding to the pairs of photoelectric conversion units inthe focus detection pixels are not stored into the memories (25(1, 2)aand 25(1, 2)b through 25(2M−1, 2M)a and 25(2M−1, 2M)b) in the secondline memory 44. In addition, since no scan signal TS2 is generatedeither, data are not sequentially provided through a serial output tothe external recipient from the second horizontal output circuit 45during the period of time elapsing until the next horizontal synchronoussignal HS is generated.

Rows selected for a partial row read or columns selected for a partialcolumn read can be adjusted based upon information transmitted from thebody drive control device 214 to the image sensor 212 in correspondenceto the position of the selected focus detection area.

Each of the switches configuring the first column switch device 47 inthe third embodiment described above selects two signals equivalent toimage-capturing pixel output signals based upon whether an odd-numberedrow or an even-numbered row in the pixel array unit 40 has been selectedvia the row scanning circuit 41 as illustrated in FIG. 28. Theindividual switches in the first column switch device 47 each sort thetwo selected signals so as to line up with the pixel arrangement assumedin the selected row and the two signals thus selected are to be storedinto the corresponding memory among the memories (28(1) through 28(2M))in the first line memory 48. However, two signals may instead be storedinto fixed memories among the memories (28(1) through 28(2M)) in thefirst line memory 48 without sorting the two selected signals to line upwith the order in which the pixels are set in the selected row. In sucha case, the scan signal TS1 can be modified to line up with the order inwhich the individual pixels are set in the selected row based uponwhether an odd-numbered row or an even-numbered row in the pixel arrayunit 40 has been selected via the row scanning circuit 41 and thememories (28(1) through 28(2M)) in the first line memory 48 can bescanned in response to the modified scan signal TS1 provided from thefirst column scanning circuit 52 to the memories (28(1) through 28(2M))in the first line memory 48.

Fourth Embodiment

The fourth embodiment is achieved as a variation of the thirdembodiment. The structure of the image sensor 212 achieved in the fourthembodiment, as shown in FIG. 31, will be described by focusing onaspects thereof characterizing the embodiment without providing anyrepeated explanation of structural features identical to those in FIG.26. The feature of the pixel array unit 40 differentiating it from thatshown in FIG. 26 is as follows. In the pixel array unit 40 shown in FIG.26, two column signal lines are installed in correspondence to eachcolumn for a total of 4M column signal lines (22(1)a and 22(1)b through22(2M)a and 22(2M)b). The structure shown in FIG. 31 is distinguishablefrom this in that the number of column signal lines installed incorrespondence to each even-numbered column is reduced to one and acolumn signal line installed for an odd-numbered column is shared withthe even-numbered column, resulting in a reduction in the overall numberof column signal lines to 3M. With the number of column signal linesreduced as described above, the wiring layout at the pixel array unit 40can be rendered less crowded in the fourth embodiment. At the same time,since this also allows the photoelectric conversion units to take up agreater area, an even higher-quality image can be generated and focusdetection can be executed with better accuracy.

In addition, as the number of column signal lines is reduced, thequantity of ADCs to configure the column A/D conversion device 42 canalso be reduced (from 4M to 3M) and thus, the structure of the imagesensor can be further simplified through the fourth embodiment.

As shown in FIG. 31, one end of each row control line 21 (21(1) through21 (2N)) corresponding to a given row is connected to an output end ofthe row scanning circuit 41 corresponding to the particular row, andcontrol signals R(1) through R(2N) are output to the respective rowcontrol lines 21.

Photoelectric conversion units in the image-capturing pixels 310 and thepairs of photoelectric conversion units 13 and 14 in the focus detectionpixels 311 disposed in a given row are connected to the row scanningcircuit 41 through the common row control line 21 and in response to acontrol signal R(L), charge storage control and signal read control areexecuted simultaneously. Two column signal lines 22(2m+1)a and 22(2m+1)bare installed at each odd-numbered column and a single column signalline 22(2m+2)a is installed at each even-numbered column in the pixelarray unit 40. The photoelectric conversion units 11 in image-capturingpixels 310 disposed at an odd-numbered column position and thephotoelectric conversion units 14 in focus detection pixels 311 disposedat the odd-numbered column position are connected to one of the twocolumn signal lines installed at the odd-numbered column, i.e., thecolumn signal line 22(2m+1)a. The photoelectric conversion units 13 inthe focus detection pixels 311 disposed at the odd-numbered columnposition are connected to the other column signal line 22(2m+1)binstalled at the odd-numbered column. In addition, the photoelectricconversion units 11 in image-capturing pixels 310 disposed at an evennumbered column position and the photoelectric conversion units 14 infocus detection pixels 311 disposed at the even-numbered column positionare connected to the column signal line 22(2m+2)a installed at theeven-numbered column. The photoelectric conversion units 13 in the focusdetection pixels 311 disposed at the even-numbered column position areconnected to the column signal line 22(2m+1)b installed at theodd-numbered column.

When an odd-numbered row in the pixel array unit 40 is selected via therow scanning circuit 41, for instance, the output signals from thephotoelectric conversion units 11 in the image-capturing pixels 310 inthe odd-numbered row are each output to the corresponding column signalline 22(2m+2)a and the output signals from the pair of photoelectricconversion units 13 and 14 in each of the focus detection pixels 311 inthe odd-numbered row are output to the corresponding column signal lines22(2m+1)a and 22(2m+1)b. When an even-numbered row in the pixel arrayunit 40 is selected via the scanning circuit 41, on the other hand, theoutput signals from the photoelectric conversion units 11 in theimage-capturing pixels 310 in the even-numbered row are each output tothe corresponding column signal line 22(2m+1)a, the output signals fromthe photoelectric conversion units 14 in the focus detection pixels 311in the even-numbered row are each output to the corresponding columnsignal line 22(2m+2)a and the output signals from the photoelectricconversion units 13 in the focus detection pixels 311 in theeven-numbered row are each output to the column signal line 22(2m+1)b.

The column A/D conversion device 42 includes 3M ADC (analog-digitalconversion) circuits 23(1)a and 23(1)b through 23(2M)a, respectivelydisposed in correspondence to the 3M column signal lines 22(1)a and22(1)b through 22(2M)a, which are installed in correspondence to theindividual pixel columns in the pixel array unit 40. In response to acontrol signal TA1 provided from the timing control circuit 50, thecolumn A/D conversion device 42 converts analog signals, output from theindividual pixels in the pixel array unit 40 in correspondence to theindividual columns, to H-bit digital signals (S(1)a and S(1)b throughS(2M)a) and outputs the digital signals resulting from the conversion.

The second column switch device 43 includes M switches 24(1, 2) through24(2M−1, 2M), each disposed in correspondence to two successive pixelcolumns. In response to a control signal TW2 provided from the timingcontrol circuit 50, the second column switch device 43 selects digitalsignals among the digital signals each output from one of the ADCs(23(1)a and 23(1)b through 23(2M)a) and outputs the selected signals.

FIGS. 32(a) and 32(b) illustrate selection operations executed at theswitch 24(2m+1, 2m+2) disposed in correspondence to two successive pixelcolumns (i.e., the (2m+1)th column and the (2m+2)th column). Threedigital signals S(2m+1)a, S(2m+1)b and S(2m+2)a are input to the switch24(2m+1, 2m+2) from the two ADCs (23(2m+1)a and 23 (2m+1)b)corresponding to the odd-numbered column (2m+1) and the single ADC(23(2m+2)a) corresponding to the even-numbered column (2m+2).

FIG. 32(a) illustrates the selection operation executed at the switch24(2m+1, 2m+2) when an odd-numbered row in the pixel array unit 40 isselected via the row scanning circuit 41. In the operation illustratedin FIG. 32(a), the three digital signals S(2m+1)a, S(2m+1)b and S(2m+2)acorresponding to the image-capturing pixel 310 disposed at theodd-numbered row/even-numbered column position and the focus detectionpixel 311 disposed at the odd-numbered row/odd-numbered column positionare input to the switch 24(2m+1, 2m+2).

In response to the control signal TW2 (indicating the odd-numbered row)input to the second column switch device 43, the switch 24(2m+1, 2m+2)selects the digital signals S(2m+1)a and S(2m+1)b corresponding to thepair of photoelectric conversion units in the focus detection pixel 311and outputs them as a pair of signals (Q(2m+1, 2m+2)a and Q(2m+1,2m+2)b) to be digitally added together.

FIG. 32(b) illustrates the selection operation executed at the switch24(2m+1, 2m+2) when an even-numbered row in the pixel array unit 40 isselected via the row scanning circuit 41. The three digital signalsS(2m+1)a, S(2m+1)b and S(2m+2)a corresponding to the image-capturingpixel 310 disposed at the even-numbered row/odd-numbered column positionand the focus detection pixel 311 disposed at the even-numberedrow/even-numbered column position are input to the switch 24(2m+1,2m+2).

In response to the control signal TW2 (indicating the even-numbered row)input to the second column switch device 43, the switch 24(2m+1, 2m+2)selects the digital signals S(2m+2)a and S(2m+1)b corresponding to thepair of photoelectric conversion units in the focus detection pixel 311and outputs them as a pair of signals (Q(2m+1, 2m+2)a and Q(2m+1,2m+2)b) corresponding to the pair of conversion units 13 and 14 in afocus detection pixel 311.

Fifth Embodiment

The fifth embodiment is achieved as an alternative with regard to thestructure of the focus detection pixels in the pixel array unit in thethird embodiment. FIG. 33 presents a layout diagram (with filtersdisposed as shown in FIG. 4) corresponding to the pixel layout diagrampresented in FIG. 25. The image sensor 212, a part of which is shown inFIG. 33, includes focus detection pixels 312 each having a pair ofphotoelectric conversion units 16 and 17 set side-by-side along thevertical direction, replacing the focus detection pixels 311 disposed ineven-numbered rows in FIG. 25.

Namely, focus detection pixels 311 are disposed at odd-numbered columnpositions and image-capturing pixels 310 are disposed at even-numberedcolumn positions in odd-numbered rows, whereas image-capturing pixels310 are disposed at odd-numbered column positions and focus detectionpixels 312 are disposed at even-numbered column positions ineven-numbered rows. Among the color filters set in the Bayer arraypattern, the green filters are all disposed at the focus detectionpixels 311 and the focus detection pixels 312, whereas the red colorfilters and the blue color filters are disposed at the image-capturingpixels 310.

FIG. 34 is a block diagram showing the structure of the image sensor 212assuming the pixel layout shown in FIG. 33. An explanation given inreference to FIG. 34 will focus on structural differences characterizingthe image sensor and an explanation of the structural elements identicalto those in FIG. 26 will not be provided. The pixel array unit 40differs from that shown in FIG. 26 in that the focus detection pixels312, each having a pair of photoelectric conversion units 16 and 17separated from each other along the vertical direction, are disposed ateven-numbered row/even-numbered column positions.

The pairs of photoelectric conversion units 16 and 17 in the individualfocus detection pixels 312 disposed at the even-numbered columnpositions in an even-numbered row are connected via a common row controlline 21, with the row scanning circuit 41. In response to a controlsignal R(L) (L is an even number), charge storage control and signalread control are simultaneously executed. One of the pair ofphotoelectric conversion units 16 and 17, i.e., the photoelectricconversion unit 16, at each of the focus detection pixels 312 disposedat the even-numbered row/even-numbered column positions is connected toone of the two column signal lines, i.e., the column signal line22(2m+2)a, installed in correspondence to the particular column. Theoutput signal (analog signal) from the photoelectric conversion unit 16is output to the column signal line 22(2m+2)a. The other photoelectricconversion unit 17 in the pair of photoelectric conversion units 16 and17 in each focus detection pixel 312 is connected to the other columnsignal line 22(2m+2)b of the two column signal lines installed incorrespondence to the particular column. The output signal (analogsignal) from the photoelectric conversion unit 17 is output to thecolumn signal line 22(2m+2)b.

Via the image sensor 212 structured as described above, a phasedifference manifesting with regard to a subject image with a contrastchange occurring along the horizontal direction can be detected basedupon a pair of sets of data obtained by grouping, along the horizontaldirection, the data from the photoelectric conversion units 13 and thedata from the photoelectric conversion units 14 in the pairs ofphotoelectric conversion units 13 and 14 in the focus detection pixels311 with green color filters, disposed at even-numbered column positionsin an odd-numbered row. In addition, a phase difference manifesting withregard to a subject image with a contrast change occurring along thevertical direction can be detected based upon a pair of sets of dataobtained by grouping, along the vertical direction, the data from thephotoelectric conversion units 16 and the data from the photoelectricconversion units 17 in the pairs of photoelectric conversion units 16and 17 in the focus detection pixels 312 with green color filters,disposed at an even-numbered column position in even-numbered rows.

Sixth Embodiment

The sixth embodiment is achieved as an alternative with regard to thestructure of the focus detection pixels in the pixel array unit in thefourth embodiment. The pixel layout adopted in the sixth embodiment isidentical to that shown in FIG. 33. The image sensor 212, a part ofwhich is shown in FIG. 33, includes focus detection pixels 312 eachhaving a pair of photoelectric conversion units 16 and 17 setside-by-side along the vertical direction, replacing the focus detectionpixels 311 disposed in even-numbered rows in FIG. 25.

Namely, focus detection pixels 311 are disposed at odd-numbered columnpositions and image-capturing pixels 310 are disposed at even-numberedcolumn positions in odd-numbered rows, whereas image-capturing pixels310 are disposed at odd-numbered column positions and focus detectionpixels 312 are disposed at even-numbered column positions ineven-numbered rows. Among the color filters set in the Bayer arraypattern, the green filters are all disposed at the focus detectionpixels 311 and the focus detection pixels 312, whereas the red colorfilters and the blue color filters are disposed at the image-capturingpixels 310.

FIG. 35 is a block diagram showing the structure of the image sensor 212assuming the pixel layout shown in FIG. 33. An explanation given inreference to FIG. 35 will focus on structural differences characterizingthe image sensor and an explanation of the structural elements identicalto those in FIG. 31 will not be provided. The pixel array unit 40differs from that shown in FIG. 31 in that the focus detection pixels312, each having a pair of photoelectric conversion units 16 and 17separated from each other along the vertical direction, are disposed ateven-numbered row/even-numbered column positions.

The pairs of photoelectric conversion units 16 and 17 in the individualfocus detection pixels 312 disposed at even-numbered column positions inan even-numbered row are connected via a common row control line 21 withthe row scanning circuit 41. In response to a control signal R(L) (L isan even number), charge storage control and signal read control aresimultaneously executed. One of the pair of photoelectric conversionunits 16 and 17, i.e., the photoelectric conversion unit 16, at each ofthe focus detection pixels 312 is connected to the one column signalline 22(2m+2)a installed for the corresponding even-numbered column. Theoutput signal (analog signal) from the photoelectric conversion unit 16is output to the column signal line 22(2m+2)a. The other photoelectricconversion unit 17 in the pair of photoelectric conversion units 16 and17 in the focus detection pixel 312 is connected to one of the twocolumn signal lines installed for an even numbered column, i.e., thecolumn signal line 22(2m+1)b. The output signal (analog signal) from thephotoelectric conversion unit 17 is output to the column signal line22(2m+1)b.

Via the image sensor 212 structured as described above, a phasedifference manifesting with regard to a subject image with a contrastchange occurring along the horizontal direction can be detected basedupon a pair of sets of data obtained by grouping, along the horizontaldirection, the data from the photoelectric conversion units 13 and thedata from the photoelectric conversion units 14 in the pairs ofphotoelectric conversion units 13 and 14 in the focus detection pixels311 with green color filters disposed at even-numbered column positionsin an odd-numbered row. In addition, a phase difference manifesting withregard to a subject image with a contrast change occurring along thevertical direction can be detected based upon a pair of sets of dataobtained by grouping, along the vertical direction, the data from thephotoelectric conversion units 16 and the data from the photoelectricconversion units 17 in the pairs of photoelectric conversion units 16and 17 in the focus detection pixels 312 with green color filtersdisposed at an even-numbered column position in even-numbered rows.

Seventh Embodiment

While the pixels (focus detection pixels and image-capturing pixels) inthe pixel array unit 40 are disposed in a square grid pattern in thepixel array unit 40 achieved in each of the first through sixthembodiments described above, the present invention may be adopted inconjunction with a pixel array pattern other than the square gridpattern.

FIG. 36 shows a pixel array adopting an array pattern sometimes referredto as a honeycomb array. This array pattern is achieved by rotating asquare grid pattern by 45°. The filter array corresponding to the pixellayout shown in FIG. 36 is shown in FIG. 37. The filter array in FIG. 37is achieved by tilting the Bayer array pattern by 45°. The honeycombarray shown in FIG. 36 and FIG. 37 includes focus detection pixels 411each having a pair of photoelectric conversion units 33 and 34 setside-by-side along the horizontal direction.

The terms “row” and “column” used in describing such a honeycomb arrayare defined as follows. Namely, a pixel row extending along thehorizontal direction formed with pixels having green color filtersdisposed thereat is an odd-numbered row, whereas a pixel row extendingalong the horizontal direction formed with pixels each having a redcolor filter or a blue color filter disposed thereat is an even-numberedrow. A pixel column extending along the vertical direction formed withpixels having green color filters disposed thereat is an odd-numberedcolumn and a pixel column extending along the vertical direction formedwith pixels each having a red color filter or a blue color filterdisposed thereat is an even-numbered column.

FIG. 38 is a block diagram showing the structure adopted in an imagesensor 212 with the pixels thereof laid out in the honeycomb array shownin FIG. 36 (2N rows×2M columns). The structure adopted for the imagesensor 212 in FIG. 38 is achieved by modifying the structure of theimage sensor shown in FIG. 10 so that focus detection pixels 411 insteadof the focus detection pixels 311 are disposed only at every otherposition in the pixel array unit 40. Namely, focus detection pixels 411are disposed only at odd-numbered column positions in an odd-numberedrow, whereas focus detection pixels 411 are disposed only ateven-numbered column positions in an even-numbered row.

At the pixel array unit 40, the focus detection pixels 411 aretwo-dimensionally arrayed over 2N rows×2M columns. The focus detectionpixel 411 in the upper left corner in FIG. 38 is the pixel taking up afirst-row/first-column position, and a green color filter is disposed atthis pixel. For this 2N row 2M column pixel array, a single row controlline 21(21(1) through 21(2N)) is wired in correspondence to each row andtwo column signal lines (22 (1)a and 22(1)b through 22(2M−1)a and22(2M−1)b) are wired in correspondence to each odd-numbered column. Oneend of each row control line 21 (21(1) through 21 (2N)) corresponding toa given row is connected to an output end of the row scanning circuit 41corresponding to the particular row, and control signals R(1) throughR(2N) are output to the respective row control lines 21.

The pairs of photoelectric conversion units 33 and 34 in the individualfocus detection pixels 411 in a given row are connected, via a commonrow control line 21, with the row scanning circuit 41. In response to acontrol signal R(L), charge storage control and signal read control aresimultaneously executed. One of the pair of photoelectric conversionunits 33 and 34, i.e., the photoelectric conversion unit 33, in thefocus detection pixel 411 disposed at an odd-numbered column position(2m+1) in an odd-numbered row is connected to one of the two columnsignal lines, i.e., the column signal line 22(2m+1)b, installed incorrespondence to the odd-numbered column (2m+1). The output signal(analog signal) from the photoelectric conversion unit 33 is output tothe column signal line 22(2m+1)b. The other photoelectric conversionunit 34 in the pair of photoelectric conversion units 33 and 34 in thefocus detection pixel 411 is connected to the other column signal line22(2m+1)a of the two column signal lines installed in correspondence tothe odd-numbered column (2m+1). The output signal (analog signal) fromthe photoelectric conversion unit 34 is output to the column signal line22(2m+1)a.

In addition, one of the pair of photoelectric conversion units 33 and34, i.e., the photoelectric conversion unit 33, in the focus detectionpixel 411 disposed at an even-numbered column position (2m+2) in aneven-numbered row is connected to one of the two column signal lines,i.e., the column signal line 22(2m+1)b, installed in correspondence tothe odd-numbered column (2m+1). The output signal (analog signal) fromthe photoelectric conversion unit 33 is output to the column signal line22(2m+1)b. The other photoelectric conversion unit 34 in the pair ofphotoelectric conversion units 33 and 34 in the focus detection pixel411 is connected to the other column signal line 22(2m+1)a of the twocolumn signal lines installed in correspondence to the odd-numberedcolumn (2m+1). The output signal (analog signal) from the photoelectricconversion unit 34 is output to the column signal line 22(2m+1).

The column A/D conversion device 42 includes ADC (analog-digitalconversion) circuits 23(1)a and 23(1)b through 23(2M−1)a and 23(2M−1)b,respectively disposed in correspondence to the column signal lines22(1)a and 22(1)b through 22(2M−1)a and 22(2M−1)b, which are installedin correspondence to pixel columns in the pixel array unit 40. Inresponse to a control signal TA1 provided from the timing controlcircuit 50, the column A/D conversion device 42 converts pairs of analogsignals output from the individual pixels in the pixel array unit 40 incorrespondence to the individual columns, to H-bit digital signals andoutputs the digital signals resulting from the conversion.

The second line memory 44 includes memories (25(1)a and 25(1)b through25(2M−1)a and 25(2M−1)b) respectively installed in correspondence to theindividual ADCs (23(1)a and 23(1)b through 23(2M−1)a and 23(2M−1)b)configuring the column A/D conversion device 42. In response to acontrol signal TM2 provided from the timing control circuit 50, thedigital signals output in correspondence to the individual ADCs (23(1)aand 23(1)b through 23(2M−1)a and 23(2M−1)b) are stored as H-bit digitalsignals into the second line memory 44. In the various memories (25(1)aand 25(1)b through 25(2M−1)a and 25(2M−1)b) in the second line memory44, the output signals from the pairs of photoelectric conversion units33 and 34 in a single row of focus detection pixels are thus stored asdigital signals.

The column digital adder device 46 includes digital adder circuits(26(1) through 26(2M−1)) each installed in correspondence to a pair ofADCs (among the pairs of ADCs (23(1)a and 23(1)b through 23(2M−1)a and23(2M−1)b) configuring the column A/D conversion device 42. In responseto a control signal TD1 provided from the timing control circuit 50, thecolumn digital adder device 46 adds together the digital signals outputfrom each pair of ADCs (among 23(1)a and 23(1)b through 23(2M−1)a and23(2M−1)b) and outputs the resulting signal as an H-bit digital sumsignal.

The first line memory 48 includes memories (28(1) through 28(2M−1))respectively installed in correspondence to the digital adder circuits(26(1) through 26(2M−1)) configuring the column digital adder device 46.In response to a control signal TM1 provided from the timing controlcircuit 50, the digital sum signals each output from one of the digitaladder circuits (26(1) through 26(2M−1)) are stored into the first linememory 48 as H-bit digital signals. Through this operation, sum signals(equivalent to output signals provided from image-capturing pixels),each obtained by adding together the output signals from the pair ofphotoelectric conversion units 33 and 34 in a focus detection pixelamong the focus detection pixels forming a single row, are stored asdigital signals in the individual memories ((28(1) through 28(2M−1)) inthe first line memory 48.

The second line memory 44 is engaged in operation in response to a scansignal TS2 provided from the second column scanning circuit 51. TheH-bit digital signals each stored in one of the memories (25(1)a and25(1)b through 25(2M−1)a and 25(2M−1)b) are read out in sequence intothe second horizontal output circuit 45, and subsequently are seriallyoutput to an external recipient as output signals (digital signals)provided via the pairs of photoelectric conversion units 33 and 34 to beused for purposes of focus detection via the second horizontal outputcircuit 45.

The first line memory 48 is engaged in operation in response to a scansignal TS1 provided from the first column scanning circuit 52. The H-bitdigital sum signals each stored in one of the memories (28(1) through28(2M−1)) are read out in sequence into the first horizontal outputcircuit 49, and subsequently are serially output to an externalrecipient as output signals (digital signals) equivalent to outputsignals provided from image-capturing pixels, via the first horizontaloutput circuit 49.

Eighth Embodiment

The eighth embodiment is achieved as an alternative with regard to thestructure of the focus detection pixels in the pixel array unit in theseventh embodiment. FIG. 39 presents a layout diagram (with filtersdisposed as shown in FIG. 37) corresponding to the pixel layout diagrampresented in FIG. 36. The image sensor 212, a part of which is shown inFIG. 39, includes focus detection pixels 412 each having a pair ofphotoelectric conversion units 36 and 37 set side-by-side along thevertical direction, replacing the focus detection pixels 411 disposed ineven-numbered rows in FIG. 36.

Namely, focus detection pixels 411 are disposed at odd-numbered columnpositions in each odd-numbered row, whereas focus detection pixels 412are disposed at even-numbered column positions in each even-numberedrow.

FIG. 40 is a block diagram showing the structure of the image sensor 212assuming the pixel layout shown in FIG. 39. An explanation given inreference to FIG. 40 will focus on structural differences characterizingthe image sensor and an explanation of the structural elements identicalto those in FIG. 38 will not be provided. The pixel array unit 40differs from that shown in FIG. 38 in that the focus detection pixels412, each having a pair of photoelectric conversion units 36 and 37,separated from each other along the vertical direction, are disposed ateven-numbered row/even-numbered column positions.

The pairs of photoelectric conversion units 36 and 37 in the individualfocus detection pixels 412 disposed at even-numbered column positions(2m+2) in an even-numbered row are connected, via a common row controlline 21, with the row scanning circuit 41. In response to a controlsignal R(L) (L is an even number), charge storage control and signalread control are simultaneously executed. One of the pair ofphotoelectric conversion units 36 and 37, i.e., the photoelectricconversion unit 36, at each of the focus detection pixels 412, isconnected to one of the two column signal lines, i.e., the column signalline 22(2m+1)a installed in correspondence to an odd-numbered column(2m+1). The output signal (analog signal) from the photoelectricconversion unit 36 is output to the column signal line 22(2m+1)a. Theother photoelectric conversion unit 37 in the pair of photoelectricconversion units 36 and 37 in the focus detection pixel 412 is connectedto the other column signal line 22(2m+1)b of the two column signal linesinstalled in correspondence to the particular odd-numbered column(2m+1). The output signal (analog signal) from the photoelectricconversion unit 37 is output to the column signal line 22(2m+1)b.

Via the image sensor 212 structured as described above, a phasedifference manifesting with regard to a subject image with a contrastchange occurring along the horizontal direction can be detected basedupon a pair of sets of data obtained by grouping, along the horizontaldirection, the data from the photoelectric conversion units 33 and thedata from the photoelectric conversion units 34 in the pairs ofphotoelectric conversion units 33 and 34 in the focus detection pixels411 with green color filters disposed at odd-numbered column positionsin an odd-numbered row. In addition, a phase difference manifesting withregard to a subject image with a contrast change occurring along thevertical direction can be detected based upon a pair of sets of dataobtained by grouping, along the vertical direction, the data from thephotoelectric conversion units 36 and the data from the photoelectricconversion units 37 in the pairs of photoelectric conversion units 36and 37 in the focus detection pixels 412 with red color filters and bluecolor filters, disposed at an even-numbered column position ineven-numbered rows.

Other Embodiments

The present invention is not limited to applications in image sensorswith focus detection pixels thereof each having two photoelectricconversion units disposed thereat, and it may be adopted in an imagesensor with focus detection pixels thereof, each having two or morephotoelectric conversion units. For instance, while the focus detectionpixel 311 shown in FIG. 6 includes two photoelectric conversion units 13and 14 defined by splitting a square into two equal portions separatedfrom each other along the horizontal direction, the present inventionmay instead be adopted in an image sensor having focus detection pixelsthereof each having four photoelectric conversion units achieved bysplitting each of the two photoelectric conversion units 13 and 14 intotwo equal portions separated from each other along the verticaldirection. In such a case, the image sensor will include, for instance,four column signal lines installed in correspondence to each column soas to allow the analog signals from the four photoelectric conversionunits to be read out independently of one another. The image sensor willfurther include a column A/D conversion device configured with ADCs thatindividually convert the analog signals output from the fourphotoelectric conversion units to digital signals and output the digitalsignals resulting from the conversion. In addition, the image sensorwill include a column digital adder device that includes digital addercircuits, via each of which the digital signals from the fourphotoelectric conversion units, output by the column A/D conversiondevice, are digitally added together. Such an image sensor will achieveadvantages similar to those of the image sensor shown in FIG. 10.

As an alternative, the image sensor may adopt a structure achieved byregarding two of the four photoelectric conversion units asphotoelectric conversion units belonging to a focus detection pixeldisposed in one of two virtual adjacent rows and regarding the remainingtwo photoelectric conversion units as photoelectric conversion unitsbelonging to a focus detection pixel in the other virtual row adjacentto the first virtual row, instead of installing four column signal lineseach in correspondence to one of the four photoelectric conversionunits. In this alternative structure, the number of column signal linescan be reduced to two. For instance, in conjunction with a focusdetection pixel 311 with four photoelectric conversion units, two ofwhich are disposed at an upper stage and the other two of which aredisposed at a lower stage, the two upper stage photoelectric conversionunits and the two lower stage photoelectric conversion units may beregarded as photoelectric conversion units belonging to focus detectionpixels in two virtual rows adjacent to each other so as to reduce thecolumn signal lines to two.

The image sensor achieved in each of the embodiments described aboveincludes a single focus detection data output channel and a single imagedata output channel installed for the entire image array unit. However,the read speed may be improved by dividing the image array unit into aplurality of areas and installing one focus detection data outputchannel and one image data output channel in correspondence to eacharea.

In the image sensor 212 achieved in each of the embodiments describedabove, the CPUa 222 in the body drive control device 214 detects thefocusing condition at the interchangeable lens 202 (optical system)based upon digital signals obtained as the column A/D conversion device42 converts pairs of analog signals to digital signals. However, thedigital signals obtained via the column A/D conversion device 42 wherethe pairs of analog signals undergo A/D conversion may instead be usedas signals for a 3-D camera.

A wiring layer may be either present or absent in the area between themicro-lenses and the photoelectric conversion units at the focusdetection pixels shown in FIG. 7. The present invention may be adoptedin an image sensor having either type of focus detection pixels. Namely,the present invention may be adopted in a backside illumination-typeimage sensor arrayed with focus detection pixels with a wiring layerdisposed on the side of the photoelectric conversion units that isopposite the side where the micro-lenses are present, as well as in animage sensor arrayed with focus detection pixels with a wiring layerinstalled between the micro-lenses and the photoelectric conversionunits. An image sensor requiring column signal lines 22, such as theimage sensor according to the present invention, is bound to include agreater number of wiring layers, in comparison to image sensors in therelated art. Since wiring layers can be disposed at a backsideillumination-type image sensor without any restrictions imposed withregard to the photoelectric conversion unit layout, the increase in thenumber of column signal lines can be accommodated with betterflexibility.

While the image sensor 212 achieved in each of the embodiments describedabove includes color filters disposed at the image-capturing pixelsthereof in the Bayer array pattern, the structures of such color filtersand the array pattern of the color filters are not limited to those inthe embodiments, and the present invention may be adopted in conjunctionwith an array of complementary color filters (green: G, yellow: Ye,magenta: Mg, cyan: Cy) or in conjunction with an arrangement other thanthe Bayer array. In addition, the present invention may be adopted in amonochromatic image sensor.

The image sensor 212 achieved in each of the embodiments describedabove, which includes the pixel array unit 40 and other components, isachieved by forming the pixel array unit 40 and the other components onseparate substrates and laminating these substrates one on top of theother. However, the present invention is not limited to this example andthe pixel array unit 40 and the other components may all the disposed ona single substrate.

It is to be noted that an image-capturing device is not limited to thedigital camera with an interchangeable lens mounted at the camera body,as described above. For instance, the present invention may instead beadopted in a digital still camera with an integrated lens or in a videocamera. Furthermore, it may also be adopted in a compact camera modulebuilt into a mobile telephone or the like, in a visual recognitiondevice in a surveillance camera or a robotic optical system, a vehicularonboard camera or the like.

The disclosure of the following priority application is hereinincorporated by reference:

-   Japanese Patent Application No. 2012-214452 filed Sep. 27, 2012

REFERENCE SIGNS LIST

-   10 micro-lens-   11, 13, 14, 16, 17, 33, 34, 36, 37 photoelectric conversion unit-   15, 18 element separation area-   21 row control line-   22 column signal line-   23 ADC (analog-digital conversion circuit)-   24, 27 switch-   25, 28 memory-   26 digital adder circuit-   29 semiconductor substrate-   30 light shielding mask-   31, 32 leveling layer-   38 color filter-   40 pixel array unit-   41 row scanning circuit-   42 column A/D conversion device-   43 second column switch device-   44 second line memory-   45 second horizontal output circuit-   46 column digital adder circuit-   47 first column switch device-   48 first line memory-   49 first horizontal output circuit-   50 timing control circuit-   51 second column scanning circuit-   52 first column scanning circuit-   71 photographic light flux-   73, 74 focus detection light flux-   90 exit pupil-   91 optical axis-   93, 94 focus detection pupil-   95 area-   100 photographic image plane-   101 focus detection area-   201 digital still camera-   202 interchangeable lens-   203 camera body-   204 mount unit-   206 lens drive control device-   208 zooming lens-   209 lens-   210 focusing lens-   211 aperture-   212 image sensor-   213 electrical contact point-   214 body drive control device-   215 liquid crystal display element drive circuit-   216 liquid crystal display element-   217 eyepiece lens-   219 memory card-   220 image sensor control unit-   221 buffer memory-   222 CPUa-   223 CPUb-   310 image-capturing pixel-   311, 312, 411, 412 focus detection pixel

The invention claimed is:
 1. An image sensor comprising: a pixel havinga first photoelectric converter and a second photoelectric converterthat convert light and generate charge; a first signal line that outputsa signal based on the charge generated by the first photoelectricconverter; a second signal line that outputs a signal based on thecharge generated by the second photoelectric converter; an adder circuitthat is connected to the first and second signal lines and that addstogether the signal based on the charge generated by the firstphotoelectric converter and the signal based on the charge generated bythe second photoelectric converter; a first output circuit that outputsat least one of the signal output by the first signal line and thesignal output by the second signal line; and a second output circuitthat outputs a sum signal generated by the adder circuit.
 2. The imagesensor according to claim 1, further comprising a first A/D converterthat is connected to the first signal line and that converts an analogsignal based on the charge generated by the first photoelectricconverter to a digital signal; and a second A/D converter that isconnected to the second signal line and that converts an analog signalbased on the charge generated by the second photoelectric converter to adigital signal.
 3. The image sensor according to claim 2, wherein theadder circuit adds together the digital signal converted by the firstA/D converter and the digital signal converted by the second A/Dconverter.
 4. The image sensor according to claim 2, wherein the firstoutput circuit outputs at least one of the digital signal obtained bythe conversion of the first A/D converter and the digital signalobtained by the conversion of the second A/D converter.
 5. The imagesensor according to claim 1, further comprising an A/D converter that isconnected to the first and second signal lines and that converts ananalog signal based on the charge generated by the first photoelectricconverter to a first digital signal and converts an analog signal basedon the charge generated by the second photoelectric converter to asecond digital signal.
 6. The image sensor according to claim 5, whereinthe adder circuit adds together the first digital signal and the seconddigital signal.
 7. The image sensor according to claim 5, wherein thefirst output circuit outputs at least one of the first digital signaland the second digital signal obtained by the conversion of the A/Dconverter.
 8. The image sensor according to claim 1, further comprisinga first memory that is connected to the first signal line and thatstores the signal based on the charge generated by the firstphotoelectric converter; and a second memory that is connected to thesecond signal line and that stores the signal based on the chargegenerated by the second photoelectric converter.
 9. The image sensoraccording to claim 8, further comprising: a first A/D converter that isconnected to the first signal line and that converts an analog signalbased on the charge generated by the first photoelectric converter to adigital signal; and a second A/D converter that is connected to thesecond signal line and that converts an analog signal based on thecharge generated by the second photoelectric converter to a digitalsignal, wherein: the first memory stores the digital signal obtained bythe conversion of the first A/D converter, and the second memory storesthe digital signal obtained by the conversion of the second A/Dconverter.
 10. The image sensor according to claim 1, further comprisinga third memory that stores the sum signal generated by the addercircuit.
 11. The image sensor according to claim 1, wherein the pixelhas a microlens, and the first and second photoelectric convertersconvert to charge light transmitting through the microlens.
 12. Animaging device comprising: the image sensor according to claim 1; and agenerator that generates image data based on the sum signal output bythe second output circuit.
 13. The image sensor according to claim 1,wherein a chip including the pixel and a chip including the addercircuit are laminated on each other.
 14. An imaging device comprising:the image sensor according to claim 1, which receives light havingpassed through an optical system; and a controller that controls aposition of the optical system based on the signal output by the firstoutput circuit as an image formed by the optical system on the imagesensor to be in focus.